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A093518 Number of ways of representing n as exactly 2 generalized pentagonal numbers. 4
1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 0, 2, 1, 2, 1, 1, 2, 0, 1, 1, 0, 2, 1, 2, 0, 1, 3, 1, 1, 1, 1, 0, 1, 1, 1, 1, 2, 1, 0, 2, 2, 2, 0, 1, 1, 0, 2, 1, 0, 1, 1, 3, 1, 0, 1, 1, 2, 2, 1, 0, 1, 2, 1, 1, 0, 2, 0, 0, 1, 2, 1, 2, 1, 0, 2, 0, 3, 1, 2, 1, 0, 2, 1, 1, 1, 1, 0, 0, 1, 0, 1, 4, 1, 1, 0, 1, 2, 0, 2, 1, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..103.

EXAMPLE

a(7)=2 as we have 7+0=5+2

PROG

(PARI) { v=vector(101); v[1]=0; for (i=1, 50, v[2*i]=i*(3*i-1)/2; v[2*i+1]=i*(3*i+1)/2); x=vector(500); for (a=1, 50, for (b=a, 50, if (v[a]+v[b]<500, x[v[a]+v[b]+1]++))); x }

CROSSREFS

Cf. A001318 (generalized pentagonal numbers), A002107 (expansion of Product (1-x^k)^2, k=1..inf.), A093519 (A093518(n)=0).

Sequence in context: A016024 A238988 A261013 * A128184 A025450 A139128

Adjacent sequences:  A093515 A093516 A093517 * A093519 A093520 A093521

KEYWORD

nonn

AUTHOR

Jon Perry, Mar 29 2004

STATUS

approved

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Last modified October 15 21:06 EDT 2018. Contains 316237 sequences. (Running on oeis4.)