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A105614
Self-convolution of A105613.
1
1, 2, 3, 6, 11, 12, 24, 48, 71, 78, 155, 272, 420, 652, 903, 1364, 2144, 3436, 5955, 9668, 10838, 16408, 27948, 45920, 66817, 109296, 152786, 197542, 327755, 531440, 735565, 1083128, 1727206, 2521374, 3938246, 5248706, 8452114, 12093692
OFFSET
0,2
EXAMPLE
Given sequence A105613:
[1, 1, 1, 2,3, 1, 6,11,12, 1, 24,48,71,78, ...],
the self-convolution yields this sequence:
[1, 2,3, 6,11,12, 24,48,71,78, ...],
which is A105613 with 1's omitted at positions {0,2,5,9,14,...}.
PROG
(PARI) {a(n)=local(V, t); if(n==0, 1, V=vector(n+1, k, t=ceil((sqrt(8*k+1)-1)/2); if(ceil((sqrt(8*k+9)-1)/2)-t==1, 1, a(k-t))); polcoeff(Ser(V)^2+x*O(x^n), n))}
CROSSREFS
Cf. A105613.
Sequence in context: A284091 A004038 A152038 * A116441 A116051 A124593
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Apr 16 2005
STATUS
approved