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%I #5 Jun 13 2017 01:36:29
%S 1,1,1,2,3,1,6,11,12,1,24,48,71,78,1,155,272,420,652,903,1,1364,2144,
%T 3436,5955,9668,10838,1,16408,27948,45920,66817,109296,152786,197542,
%U 1,327755,531440,735565,1083128,1727206,2521374,3938246,5248706,1,8452114
%N Self-convolution omits 1's at positions of triangular numbers less one.
%C Self-convolution is A105614.
%e Given this sequence:
%e A = [1, 1, 1, 2,3, 1, 6,11,12, 1, 24,48,71,78, 1, 155, ...],
%e the self-convolution yields:
%e A^2 = [1, 2,3, 6,11,12, 24,48,71,78, 155,272,420,652,903, ...],
%e giving this sequence with 1's omitted at positions {0,2,5,9,14,...}.
%o (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)))
%Y Cf. A105614.
%K nonn
%O 0,4
%A _Paul D. Hanna_, Apr 16 2005
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