OFFSET
1,1
COMMENTS
Vaguely related to odd perfect numbers - they must have one prime 1 mod 4 with an exponent 1 mod 4.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
29 == 1 mod 4 and 29+1 = 30 = 2*3*5 has 5 == 1 mod 4 as a prime factor.
MAPLE
filter:= proc(n) isprime(n) and has(1, numtheory:-factorset(n+1) mod 4) end proc:
select(filter, [seq(i, i=1..2000, 4)]); # Robert Israel, Mar 13 2020
MATHEMATICA
Select[Prime[Range[500]], Mod[# - 1, 4] == 0 && Sort[Mod[Transpose[FactorInteger[# + 1]][[1]] - 1, 4]][[1]] == 0 &] (* T. D. Noe, Jan 25 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, Jan 25 2013
STATUS
approved