OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = 6*A202607(n). - Ivan N. Ianakiev, Feb 07 2022
EXAMPLE
a(3) = 462 is a term because sigma(462) = 1152 and 461, 463, 1151 and 1153 are primes.
MAPLE
filter:= proc(x) local t;
if not (isprime(x-1) and isprime(x+1)) then return false fi;
t:= numtheory:-sigma(x);
t mod 6 = 0 and isprime(t-1) and isprime(t+1)
end proc:
select(filter, [seq(i, i=6..100000, 6)]);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Feb 06 2022
STATUS
approved