A074821 - OEIS

A074821

Numbers k such that tau(k) = tau(2k+1).

2, 3, 4, 5, 10, 11, 23, 27, 29, 34, 38, 41, 46, 53, 55, 57, 62, 76, 77, 83, 89, 91, 93, 106, 113, 118, 123, 129, 131, 133, 136, 143, 145, 159, 161, 173, 177, 179, 185, 191, 201, 203, 205, 206, 212, 213, 218, 226, 232, 233, 235, 239, 251, 259, 267, 281, 291, 293

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OFFSET

1,1

COMMENTS

If a term is a perfect square, then its square root must be in A001542. The first few such terms are the squares of 2, 2378, 93222358, 165326326037771920630... - Ivan Neretin, May 25 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10014

MATHEMATICA

Select[Range[300], DivisorSigma[0, #] == DivisorSigma[0, 2 # + 1] &] (* Ivan Neretin, May 25 2016 *)

CROSSREFS

Sequence in context: A375460 A348255 A117360 * A348511 A338897 A296160

Adjacent sequences: A074818 A074819 A074820 * A074822 A074823 A074824

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Sep 08 2002

STATUS

approved