OFFSET
1,3
MAPLE
s := n -> if irem(n, 2) = 1 and (isprime(n) or issqr(n)) then (n-1)/2 else NULL fi:
seq(s(n), n=0..241);
MATHEMATICA
Select[Range[0, 120], Or[IntegerQ@ Sqrt@ #, PrimeQ@ #] &[2 # + 1] &] (* Michael De Vlieger, Jul 15 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Jul 15 2019
STATUS
approved