A324723 Numbers n such that bitor(2*k, sigma(k)) == 2k, where k = A156552(n).

4, 8, 9, 16, 27, 30, 32, 45, 64, 72, 125, 128, 135, 144, 243, 250, 256, 270, 315, 405, 420, 480, 490, 512, 576, 600, 675, 756, 810, 825, 875, 988, 1000, 1024, 1152, 1155, 1210, 1215, 1458, 1470, 1600, 1690, 1716, 1728, 1920, 2048, 2100, 2187, 2250, 2430, 2450, 2475, 3125, 3234, 3240, 3600, 3645, 3825, 4320, 4375, 5070, 5103

Offset

1,1

Links

Table of n, a(n) for n=1..62.

Index entries for sequences related to binary expansion of n

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Prog

(PARI)
A156552(n) = {my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res}; \\ From A156552 by David A. Corneth
isA324726(n) = ((2*n)==bitor(2*n, sigma(n)));
isA324723(n) = if(n>1, isA324726(A156552(n)));
(PARI) isA324723(n) = if(1==n, 0, my(t=2*A156552(n)); (t==bitor(t, A323243(n)))); \\ Using also code from A323243.

Crossrefs

Cf. A156552, A323243, A324722, A324726.

Sequence in context: A371010 A067252 A348995 * A355580 A272758 A227645

Adjacent sequences: A324720 A324721 A324722 * A324724 A324725 A324726

Keyword

nonn

Author

Antti Karttunen, Mar 15 2019

Status

approved