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 A270528 Sum of divisors of the products of the smaller and larger parts of the partitions of n into two parts. 1
 0, 1, 3, 11, 19, 34, 58, 91, 120, 167, 245, 296, 413, 471, 574, 731, 948, 961, 1335, 1395, 1645, 1872, 2398, 2344, 2994, 3109, 3603, 3865, 4865, 4388, 5960, 5851, 6608, 7006, 8189, 7811, 10203, 9806, 11000, 11147, 13930, 12216, 16093, 15118, 16459, 17459 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS FORMULA a(n) = Sum_{i=1..floor(n/2)} sigma(i*(n-i)). EXAMPLE a(5) = 19; the partitions of 5 into two parts are (1,4) and (2,3). The sum of divisors of the products of the partitions is sigma(4) + sigma(6) = (1+2+4) + (1+2+3+6) = 7 + 12 = 19. MAPLE with(numtheory): A270528:=n->add(sigma(i*(n-i)), i=1..floor(n/2)): seq(A270528(n), n=1..100); MATHEMATICA Table[Sum[DivisorSigma[1, i*(n - i)], {i, Floor[n/2]}], {n, 80}] PROG (PARI) a(n) = sum(i=1, n\2, sigma(i*(n-i))); \\ Michel Marcus, Mar 18 2016 CROSSREFS Cf. A000203, A253275. Sequence in context: A014223 A023265 A018557 * A213540 A085616 A138723 Adjacent sequences:  A270525 A270526 A270527 * A270529 A270530 A270531 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Mar 18 2016 STATUS approved

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Last modified May 24 06:53 EDT 2019. Contains 323529 sequences. (Running on oeis4.)