A181615 - OEIS

A181615

Triangle read by rows: T(n,k) = 2^(n-1) mod semiprime(k).

1, 2, 2, 0, 4, 4, 0, 2, 8, 8, 0, 4, 7, 6, 2, 0, 2, 5, 2, 4, 2, 0, 4, 1, 4, 8, 4, 1, 0, 2, 2, 8, 2, 8, 2, 18, 0, 4, 4, 6, 4, 1, 4, 14, 6, 0, 2, 8, 2, 8, 2, 8, 6, 12, 18, 0, 4, 7, 4, 2, 4, 16, 12, 24, 10, 1, 0, 2, 5, 8, 4, 8, 11, 2, 23, 20, 2, 8, 0, 4, 1, 6, 8, 1, 1, 4, 21, 14, 4

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..89.

EXAMPLE

Triangle begins:

2, 2;

0, 4, 4;

0, 2, 8, 8;

0, 4, 7, 6, 2;

...

MATHEMATICA

Table[PowerMod[2, n-1, #[[;; n]]], {n, Length[#]}] & [Select[Range[50], PrimeOmega[#] == 2 &]] (* Paolo Xausa, Jun 29 2024 *)

PROG

(PARI) trg(nn) = {semip = select(n->bigomega(n) == 2, vector(nn, i, i)); for (n = 1, #semip, for (k = 1, n, print1(2^(n-1) % semip[k], ", "); ); print(); ); } \\ Michel Marcus, Sep 11 2013

CROSSREFS

Cf. A173622, A181670.

Sequence in context: A276275 A128585 A217840 * A141333 A262967 A168090

Adjacent sequences: A181612 A181613 A181614 * A181616 A181617 A181618

KEYWORD

nonn,tabl

AUTHOR

Juri-Stepan Gerasimov, Dec 02 2010

EXTENSIONS

Corrected by T. D. Noe, Dec 02 2010

STATUS

approved