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
KEYWORD
sign
AUTHOR
Michel Marcus, Oct 29 2021
STATUS
approved