A072275 Least m such that one less than m-th prime has n divisors (or 0 if no such prime exists).

2, 3, 4, 7, 6, 0, 11, 12, 30, 0, 18, 0, 44, 79, 47, 0, 42, 0, 53, 106, 1581, 0, 82, 211, 1470, 595, 319, 0, 169, 0, 216, 2819, 177975, 38836904, 279, 0, 62947, 41203, 326, 0, 647, 0, 1795, 907, 8719625, 0, 369, 0, 841, 12545382, 6180, 0, 820, 190066763704011

Offset: 2

Author

Lekraj Beedassy, Jul 09 2002

Keywords

• nonn

Crossrefs

A000040(a(n)) = A066814(n).

Programs

Mathematica

Do[ If[ !PrimeQ[n], k = 1; While[ Length[ Divisors[ Prime[k] - 1]] != n, k++ ]; Print[k], Print[0]], {n, 6, 34}]

Extensions

More terms from Robert G. Wilson v, Jul 15 2002

a(35) inserted and a(46)-a(55) added by Amiram Eldar, Feb 06 2019