A340720 Least positive number k such that sigma(k) = n * sigma(k+1).
14, 12, 180, 25908120
Offset: 1
Examples
n | sigma(a(n)) | sigma(a(n)+1) ----+-------------+-------------- 1 | 24 | 24 2 | 28 | 14 3 | 546 | 182 4 | 103680000 | 25920000
Programs
-
PARI
{a(n) = my(k=1); while(sigma(k)!=n*sigma(k+1), k++); k}