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 A105613 Self-convolution omits 1's at positions of triangular numbers less one. 1
 1, 1, 1, 2, 3, 1, 6, 11, 12, 1, 24, 48, 71, 78, 1, 155, 272, 420, 652, 903, 1, 1364, 2144, 3436, 5955, 9668, 10838, 1, 16408, 27948, 45920, 66817, 109296, 152786, 197542, 1, 327755, 531440, 735565, 1083128, 1727206, 2521374, 3938246, 5248706, 1, 8452114 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Self-convolution is A105614. LINKS EXAMPLE Given this sequence: A = [1, 1, 1, 2,3, 1, 6,11,12, 1, 24,48,71,78, 1, 155, ...], the self-convolution yields: A^2 = [1, 2,3, 6,11,12, 24,48,71,78, 155,272,420,652,903, ...], giving this sequence with 1's omitted at positions {0,2,5,9,14,...}. PROG (PARI) a(n)=local(V, t); if(n==0 || n==1, 1, t=ceil((sqrt(8*n+9)-1)/2); if(ceil((sqrt(8*n+17)-1)/2)-t==1, 1, V=vector(n-t+2, k, a(k-1)); polcoeff(Ser(V)^2+O(x^(n-t+2)), n-t+1))) CROSSREFS Cf. A105614. Sequence in context: A130534 A008275 A107416 * A334951 A263634 A135894 Adjacent sequences:  A105610 A105611 A105612 * A105614 A105615 A105616 KEYWORD nonn AUTHOR Paul D. Hanna, Apr 16 2005 STATUS approved

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Last modified June 18 18:17 EDT 2021. Contains 345120 sequences. (Running on oeis4.)