The On-Line Encyclopedia of Integer Sequences (OEIS)

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The On-Line Encyclopedia of Integer Sequences (OEIS)

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Revision History for A330821

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

a(1) = 1, a(2) = 2. Thereafter a(n+1) is the smallest number k such that A001414(k) = a(n) + a(n-1).
(history; published version)

#48 by Peter Luschny at Mon Mar 09 15:32:53 EDT 2020

STATUS

reviewed

approved

#47 by Michel Marcus at Mon Mar 09 14:06:42 EDT 2020

STATUS

proposed

reviewed

#46 by Jinyuan Wang at Sun Mar 08 20:32:51 EDT 2020

STATUS

editing

proposed

#45 by Jinyuan Wang at Sun Mar 08 20:30:14 EDT 2020

DATA

1, 2, 3, 5, 15, 51, 305, 1059, 4083, 117737, 3775459, 19465955, 952896293, 13613071346, 14565967639, 112716155924, 11073544747197, 637616871476643, 11027737075804991, 3056322734187753262, 720827360746936177235, 2895534733924495721972, 184434466828243026858537, 12176450101540888967731915542921033413649799807, 8189660342217563295915, 515222301162241572644117

LINKS

Jinyuan Wang, <a href="/A330821/b330821.txt">Table of n, a(n) for n = 1..200</a>

EXTENSIONS

Data corrected by Jinyuan Wang, Mar 08 2020

STATUS

proposed

editing

Discussion

Sun Mar 08

20:32

Jinyuan Wang: I've emailed David yesterday, but maybe he didn't see it

#44 by Jinyuan Wang at Sun Mar 08 04:05:30 EDT 2020

STATUS

editing

proposed

Discussion

Sun Mar 08

04:10

Michel Marcus: you mean "formula or data"  ?

04:11

Michel Marcus: we should ask Amiram ?

05:08

Michel Marcus: then talk with David A. Corneth

06:07

Amiram Eldar: I have calculated just the first 12 terms up to 19465955...

06:13

Jinyuan Wang: you just need to know A001414(542921033413649799807) = a(19) + a(20) is right, and 542921033413649799807 < 720827360746936177235. so a(21) must be not correct. After seeing  A056240, I'm sure the formula is right and data isn't right.

10:32

Giovanni Resta: I agree with Jinyuan Wang, a(21) is incorrect and probably it is equal to 542921033413649799807.

#43 by Jinyuan Wang at Sun Mar 08 03:59:43 EDT 2020

NAME

a(1) = 1, a(2) = 2. Thereafter a(n+1) is the smallest number k such that A001414(k) = a(n) + a(n-1).

FORMULA

a(n+1) = A056240(a(n) + a(n-1)).

EXAMPLE

sopfr(3) = 3 = 2 + 1, sopfr(15) = 8 = 3 + 5, etc.

KEYWORD

nonn,more,new

STATUS

approved

editing

Discussion

Sun Mar 08

04:05

Jinyuan Wang: formula or date is not correct. if formula is right, then a(21) should be 542921033413649799807. who can judge this ?

#42 by N. J. A. Sloane at Sun Feb 23 17:50:20 EST 2020

STATUS

editing

approved

#41 by N. J. A. Sloane at Sun Feb 23 17:50:17 EST 2020

NAME

a(1)=1, a(2)=2. Thereafter, a(n+1) is the smallest number k such that A001414(k) = a(n) + a(n-1).

EXTENSIONS

Data corrected by and more terms from Amiram Eldar and David A. Corneth, Jan 02 2020

STATUS

proposed

editing

#40 by David A. Corneth at Wed Jan 08 08:02:38 EST 2020

STATUS

editing

proposed

#39 by David A. Corneth at Wed Jan 08 08:01:22 EST 2020

PROG

(PARI) first(n) = {n = max(2, n); my(res = vector(n), p, c); res[1] = 1; res[2] = 2; for(i = 3, n, c = res[i-2] + res[i-1]; if(isprime(c), res[i] = c; next); p = precprime(c); while(!isprime(c - p), p = precprime(p - 1)); res[i] = p * (c - p)

); res} \\ David A. Corneth, Jan 02 2020

STATUS

proposed

editing

Discussion

Wed Jan 08

08:02

David A. Corneth: I slipped but hadn't removed the code I used there. The numbers I put are from a different code-sample.