A242920 Numbers N with prime factors p_1, ... p_n, such that 1/p_1 + Sum_{i=2..n} p_(i-1)/p_i + p_n/N - (n+2)/N = 1.

6, 10, 14, 15, 22, 26, 34, 35, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 143, 146, 158, 166, 178, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 323, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458, 466, 478

Offset

1,1

Links

Table of n, a(n) for n=1..55.

Steve Humble, Create your own mathematical mysteries, +plus magazine, University of Cambridge.

Example

6=2*3 and 1/2 + 2/3 + 3/6 - 4/6 = 1, so 6 belongs to the sequence.

Prog

(PARI) isok(n) = f = factor(n)[, 1]; 1/f[1] + sum(i=2, #f, f[i-1]/f[i]) + f[#f]/n - (#f~ + 2)/n == 1;

Crossrefs

Sequence in context: A371811 A162409 A226494 * A183072 A225704 A228301

Adjacent sequences: A242917 A242918 A242919 * A242921 A242922 A242923

Keyword

nonn

Author

Michel Marcus, May 26 2014

Status

approved