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A348689
a(n) = sigma(n) + sigma(n+1) - sigma(n+2), where sigma is the sum of divisors.
2
0, 0, 5, 1, 10, 5, 10, 10, 19, 2, 26, 18, 14, 17, 37, 10, 37, 17, 30, 38, 44, 0, 53, 49, 33, 26, 66, 14, 70, 41, 47, 57, 54, 11, 101, 69, 42, 26, 104, 36, 94, 56, 50, 90, 102, -4, 115, 88, 78, 67, 116, 32, 102, 72, 112, 110, 110, -18, 166, 134, 54, 73, 147, 67, 160, 86, 98, 78, 168, 21
OFFSET
1,3
LINKS
MATHEMATICA
Array[#+#2-#3&@@DivisorSigma[1, {#, #+1, #+2}]&, 100] (* Giorgos Kalogeropoulos, Oct 29 2021 *)
PROG
(PARI) a(n) = sigma(n)+sigma(n+1) - sigma(n+2);
CROSSREFS
KEYWORD
sign
AUTHOR
Michel Marcus, Oct 29 2021
STATUS
approved