2,1

Table of n, a(n) for n=2..86.

a(8) = 2 as prime(8) = 17 and 17-1 = 2^4.

a(10) = 7 as prime(10) = 29 and 29-1 =28 = 2*7^2.

Sequence in context: A185688 A203955 A039638 * A023503 A241195 A039640

Adjacent sequences: A090923 A090924 A090925 * A090927 A090928 A090929

base,easy,nonn

Amarnath Murthy, Dec 26 2003

More terms from Erich Friedman, Aug 08 2005

approved