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A348688
a(n) = sigma(n) + sigma(n+1) + sigma(n+2) - sigma(n+3), where sigma is the sum of divisors.
3
1, 8, 5, 17, 11, 22, 18, 34, 15, 44, 30, 42, 31, 61, 34, 68, 35, 69, 58, 86, 32, 89, 73, 93, 57, 108, 54, 126, 71, 119, 89, 117, 59, 155, 117, 133, 64, 164, 92, 184, 98, 146, 134, 186, 74, 187, 136, 202, 124, 209, 104, 200, 126, 232, 182, 230, 62, 256, 194, 222, 135, 243, 171, 287, 170
OFFSET
1,2
LINKS
MATHEMATICA
Array[#+#2+#3-#4&@@DivisorSigma[1, {#, #+1, #+2, #+3}]&, 100] (* Giorgos Kalogeropoulos, Oct 29 2021 *)
PROG
(PARI) a(n) = sigma(n) + sigma(n+1) + sigma(n+2) - sigma(n+3);
CROSSREFS
Cf. A000203, A348335, A348689, A348698 (a(n) <= 0).
Sequence in context: A193681 A347902 A253806 * A199806 A070484 A096480
KEYWORD
sign
AUTHOR
Michel Marcus, Oct 29 2021
STATUS
approved