A247137 Numbers for which the root mean square of nontrivial divisors is an integer and which are not a square of prime numbers.

119, 161, 343, 369, 527, 711, 721, 833, 959, 1081, 1127, 1241, 1695, 1767, 2047, 3281, 3335, 3553, 3713, 4207, 4633, 4681, 5047, 5215, 6713, 6887, 7327, 7775, 9641, 12319, 14031, 16617, 16999, 18473, 19199, 22145, 27009, 27913, 29449, 31679, 32239, 32599, 37241, 44801, 45385, 47865, 47959, 50279, 52319, 56033

Offset

1,1

Comments

That's the numbers which are in A247136 and not in A001248.

Links

Daniel Lignon and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (terms up to 148 from Lignon)

Prog

(PARI) integralRMS(v)=my(t=norml2(v)/#v); denominator(t)==1 && issquare(t)
is(n)=my(d=divisors(n)); #d>3 && integralRMS(d[2..#d-1]) \\ Charles R Greathouse IV, Nov 20 2014

Crossrefs

Cf. A247136 (Numbers for which the root mean square of nontrivial divisors is an integer).

Sequence in context: A135716 A026049 A273179 * A134603 A134604 A255580

Adjacent sequences: A247134 A247135 A247136 * A247138 A247139 A247140

Keyword

nonn

Author

Daniel Lignon, Nov 20 2014

Status

approved