A348688 a(n) = sigma(n) + sigma(n+1) + sigma(n+2) - sigma(n+3), where sigma is the sum of divisors.

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

Michel Marcus, Table of n, a(n) for n = 1..11000

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

Adjacent sequences: A348685 A348686 A348687 * A348689 A348690 A348691

Keyword

sign

Author

Michel Marcus, Oct 29 2021

Status

approved