A070225 Numbers k such that (sigma(k)-k) - Sum_{p|k} p^2 = -1.

4, 45, 175, 1573, 5491, 26071, 72283, 212341, 367993, 1050703, 1247941, 2608891, 3352351, 5799421, 7040833, 7722991, 11800141, 13766161, 19609831, 22345963, 30273673, 42022741, 73911181, 80434513, 98397223, 141963643, 184867531, 215639401, 235646491, 264196483

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Formula

a(1)=4; a(n+1) = A001359(n)^2*(A001359(n)+2) where A001359 lists number that are the lesser of twin primes.

Prog

(PARI) for(n=1, 1000000, if(sumdiv(n, d, d)-n+1-sumdiv(n, d, isprime(d)*d^2)==0, print1(n, ", ")))

Crossrefs

Sequence in context: A173327 A075029 A369228 * A132998 A120075 A273832

Adjacent sequences: A070222 A070223 A070224 * A070226 A070227 A070228

Keyword

easy,nonn

Author

Benoit Cloitre, May 07 2002

Status

approved