A247142 Numbers for which the root mean square of proper divisors is an integer.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 35, 37, 41, 43, 47, 49, 53, 55, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 145, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 215, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 341

Offset

1,1

Comments

All the prime numbers (A000040) are in this sequence. But there are other numbers (A247135).

Links

Daniel Lignon, Table of n, a(n) for n = 1..1249

Mathematica

Select[Range[2, 1000], IntegerQ[RootMeanSquare[Most[Divisors[#]]]]&]

Crossrefs

Cf. A140480 (RMS of all divisors is an integer).

Sequence in context: A371654 A089063 A339819 * A350342 A369093 A171019

Adjacent sequences: A247139 A247140 A247141 * A247143 A247144 A247145

Keyword

nonn

Author

Daniel Lignon, Nov 20 2014

Status

approved