A100037 - OEIS

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A100037 - OEIS

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A100037

Positions of occurrences of the natural numbers as a second subsequence in A100035.

21

4, 9, 18, 31, 48, 69, 94, 123, 156, 193, 234, 279, 328, 381, 438, 499, 564, 633, 706, 783, 864, 949, 1038, 1131, 1228, 1329, 1434, 1543, 1656, 1773, 1894, 2019, 2148, 2281, 2418, 2559, 2704, 2853, 3006, 3163, 3324, 3489, 3658, 3831, 4008, 4189, 4374, 4563

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OFFSET

1,1

COMMENTS

For n > 1, A100035(a(n)) = n and A100035(m) != n for a(n-1) <= m < a(n);

A100036(n) < a(n) < A100038(n) < A100039(n).

LINKS

Table of n, a(n) for n=1..48.

Guo-Niu Han, Enumeration of Standard Puzzles, 2011. [Cached copy]

Guo-Niu Han, Enumeration of Standard Puzzles, arXiv:2006.14070 [math.CO], 2020.

FORMULA

a(n) = 2*n^2 - n + 3 (conjectured). - Ralf Stephan, May 15 2007

EXAMPLE

First terms (10 = A, 11 = B, 12 = C) of A100035(a(n)):

...1....2........3............4................5......

1231435425165764736271879869584938291A9BA8B7A6B5A4B3A2B;

a(1) = A084849(2) = 4, A100035(4) = 1;

a(2) = A014107(2) = 9, A100035(9) = 2;

a(3) = A033537(3) = 18, A100035(18) = 3;

a(4) = A100040(4) = 31, A100035(31) = 4;

a(5) = A100041(5) = 48, A100035(48) = 5.

CROSSREFS

Cf. A014107, A033537, A084849, A100035, A100036, A100038, A100039, A100040, A100041.

Sequence in context: A301017 A008219 A008223 * A063916 A009855 A038402

Adjacent sequences: A100034 A100035 A100036 * A100038 A100039 A100040

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 31 2004

STATUS

approved