A054964 Numbers whose divisors have the form m^k + 1, k>1.

1, 2, 5, 10, 17, 37, 101, 197, 257, 401, 577, 677, 1297, 1601, 2917, 3137, 4357, 5477, 7057, 8101, 8837, 12101, 13457, 14401, 15377, 15877, 16901, 17957, 21317, 22501, 24337, 25601, 28901, 30977, 32401, 33857, 41617, 42437, 44101, 50177

Offset

1,2

Links

Jean-François Alcover, Table of n, a(n) for n = 1..10002

Example

1 =0*0+1, 2 = 1*1+1, 5 = 2*2+1, 10 = 3*3+1 = 2*5, 17 = 4*4+1, ...

Mathematica

okQ[n_] := n==1 || n==10 || PrimeQ[n] && IntegerQ[Sqrt[n-1]]; (* Jean-François Alcover, Nov 21 2019, after Charles R Greathouse IV *)

Prog

(PARI) is(n)=(isprime(n) && issquare(n-1)) || n==1 || n==10 \\ Charles R Greathouse IV, Mar 11 2014

Crossrefs

A002496 together with 1 and 10: a(n+5)=A002496(n+3).

Sequence in context: A308604 A018315 A146220 * A057752 A342604 A173057

Adjacent sequences: A054961 A054962 A054963 * A054965 A054966 A054967

Keyword

nonn,easy,nice

Author

Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), May 24 2000

Status

approved