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 A191831 a(n) = Sum_{i+j=n, i,j >= 1} tau(i)*sigma(j), where tau() = A000005(), sigma() = A000203(). 4
 0, 1, 5, 12, 24, 39, 60, 87, 113, 158, 189, 249, 286, 372, 402, 516, 545, 696, 709, 886, 912, 1125, 1110, 1401, 1348, 1674, 1654, 1992, 1906, 2390, 2226, 2735, 2648, 3141, 2926, 3705, 3346, 4069, 3898, 4604, 4223, 5282, 4707, 5757, 5426, 6326, 5754, 7269, 6324, 7669, 7230, 8468, 7556, 9456, 8240, 10018, 9320, 10748, 9621, 12246 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This is Andrews's D_{0,1}(n). From Omar E. Pol, Dec 08 2021: (Start) Zero together with the convolution of A000005 and A000203. Zero together with the convolution of A341062 and A024916. Zero together with the convolution of the nonzero terms of A006218 and A340793. a(n) is also the volume of a symmetric polycube which belongs to the family of symmetric polycubes that represent the convolution of A000203 with any other integer sequence, n >= 1. (End) LINKS George E. Andrews, Stacked lattice boxes, Ann. Comb. 3 (1999), 115-130. FORMULA G.f.: (Sum_{k>=1} x^k/(1 - x^k))*(Sum_{k>=1} k*x^k/(1 - x^k)). - Ilya Gutkovskiy, Jan 01 2017 MAPLE with(numtheory); D01:=n->add(tau(j)*sigma(n-j), j=1..n-1); [seq(D01(n), n=1..60)]; MATHEMATICA Table[Sum[DivisorSigma[0, j] DivisorSigma[1, n - j], {j, n - 1}], {n, 60}] (* Michael De Vlieger, Jan 01 2017 *) PROG (PARI) a(n)=sum(i=1, n-1, numdiv(i)*sigma(n-i)) \\ Charles R Greathouse IV, Feb 19 2013 CROSSREFS Cf. A000005, A000203 A006218, A024916, A086718, A237593, A340793, A341062. Sequence in context: A100479 A018806 A101425 * A188182 A187210 A299901 Adjacent sequences: A191828 A191829 A191830 * A191832 A191833 A191834 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jun 17 2011 STATUS approved

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Last modified December 6 04:35 EST 2022. Contains 358594 sequences. (Running on oeis4.)