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

Author

Jaroslav Krizek, May 29 2014

Keywords

• nonn

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).

Examples

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

Links

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

Crossrefs

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

Programs

Magma

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

Mathematica

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