A280935 Numbers k such that k = rad(k) * sopfr(k), where rad(k) is the squarefree kernel of k and sopfr(k) the integer log of k.

16, 27, 72, 540, 2106, 2625, 3264, 5445, 5824, 5880, 10647, 13475, 15210, 15500, 18048, 22800, 28611, 37752, 38528, 39445, 42237, 47334, 61568, 64141, 68952, 69575, 70308, 71136, 71478, 72912, 74115, 75392, 79000, 80937, 83712, 89775, 100156, 100359, 113680, 114660

Offset

1,1

Links

Paolo P. Lava, Table of n, a(n) for n = 1..500

Example

Prime factors of 2106 are 2, 3, 3, 3, 3, 13. Then rad(2106) = 2 * 3 * 13 = 78, sopfr(2106) = 2 + 3 + 3 + 3 + 3 + 13 = 27 and 78 * 27 = 2106.

Maple

with(numtheory): P:=proc(q) local a, k, n; for n from 1 to q do a:=ifactors(n)[2];
if n=mul(a[k][1], k=1..nops(a))*add(a[k][1]*a[k][2], k=1..nops(a)) then print(n);
fi; od; end: P(10^9);

Crossrefs

Cf. A001414, A007947, A068999.

Sequence in context: A032610 A286429 A329206 * A067650 A123963 A073396

Adjacent sequences: A280932 A280933 A280934 * A280936 A280937 A280938

Keyword

nonn,easy

Author

Paolo P. Lava, Jan 11 2017

Status

approved