A242962 a(1) = a(2) = 0; for n >= 3: a(n) = (n*(n+1)/2) mod antisigma(n) = A000217(n) mod A024816(n).

0, 0, 0, 1, 6, 3, 8, 15, 13, 18, 12, 28, 14, 24, 24, 31, 18, 39, 20, 42, 32, 36, 24, 60, 31, 42, 40, 56, 30, 72, 32, 63, 48, 54, 48, 91, 38, 60, 56, 90, 42, 96, 44, 84, 78, 72, 48, 124, 57, 93, 72, 98, 54, 120, 72, 120, 80, 90, 60, 168, 62, 96, 104, 127, 84

Offset

1,5

Comments

A000217(n) = triangular numbers, A024816(n) = sum of numbers less than n which do not divide n.

a(n) = sigma(n) = A000203(n) for n = 5 and n>= 7 (see A242963).

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Example

a(6) = 3 because A000217(6) mod A024816(6) = 21 mod 9 = 3.

Mathematica

Array[If[# < 3, 0, Mod[PolygonalNumber@ #, Total@ Complement[Range@ #, Divisors@ #]]] &, 65] (* Michael De Vlieger, Jan 28 2020 *)

Prog

(Magma) [((n*(n+1)div 2) mod (n*(n+1)div 2-SumOfDivisors(n))): n in [3..1000]]

Crossrefs

Cf. A000217, A002961, A024816, A242963, A243117, A243118.

Sequence in context: A271179 A220085 A242013 * A257938 A153632 A308170

Adjacent sequences: A242959 A242960 A242961 * A242963 A242964 A242965

Keyword

nonn

Author

Jaroslav Krizek, May 29 2014

Status

approved