A152989 Sum of proper divisors minus the number of proper divisors of triangular number A000217(n).

0, 0, 3, 5, 6, 8, 23, 47, 28, 14, 71, 83, 18, 80, 225, 127, 76, 84, 163, 351, 146, 32, 385, 551, 104, 202, 567, 307, 278, 296, 487, 941, 296, 262, 1219, 805, 54, 372, 1549, 933, 476, 498, 631, 1795, 826, 68, 1737, 2221, 534, 946, 1683, 883, 722, 1380, 2469, 2861, 740, 86, 2535

Offset

1,3

Links

B. D. Swan, Table of n, a(n) for n=1,...,10000

Formula

a(n) = A001065(A000217(n)) - A032741(A000217(n)) = A152770(A000217(n)).

Mathematica

DivisorSigma[1, #]-DivisorSigma[0, #]-#+1&/@Accumulate[Range[60]] (* Harvey P. Dale, May 06 2014 *)

Prog

(PARI) a(n) = sigma(n*(n+1)/2) - n*(n+1)/2 - (numdiv(n*(n+1)/2) - 1); \\ Michel Marcus, Jan 28 2014

Crossrefs

Cf. A000005, A000203, A000217, A001065, A032741, A152770.

Sequence in context: A102989 A005623 A335110 * A308051 A261028 A195481

Adjacent sequences: A152986 A152987 A152988 * A152990 A152991 A152992

Keyword

nonn

Author

Omar E. Pol, Dec 20 2008

Status

approved