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
KEYWORD
nonn,easy,nice
AUTHOR
Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), May 24 2000
STATUS
approved