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A242962
a(1) = a(2) = 0; for n >= 3: a(n) = (n*(n+1)/2) mod antisigma(n) = A000217(n) mod A024816(n).
5
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
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
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, May 29 2014
STATUS
approved