A211659 Numbers k such that k and k+1 both have unique values of sigma(k) and sigma(k+1); sigma(k) = A000203(k) = sum of divisors of k.

1, 2, 3, 4, 7, 8, 12, 18, 36, 49, 72, 100, 128, 133, 148, 162, 192, 199, 217, 218, 256, 288, 313, 337, 400, 421, 457, 511, 547, 548, 562, 576, 577, 578, 652, 661, 676, 721, 841, 842, 871, 876, 1058, 1093, 1152, 1171, 1191, 1200, 1227, 1233, 1249, 1282, 1306

Offset

1,2

Comments

Subsequence of A211656. Number k is in sequence iff k and k+1 are in A211656.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

Number 36 is in sequence because sigma(36) = 91, sigma(37) = 38 and there are no other numbers m, n with sigma(m) = 91 or sigma(n) = 38.

Crossrefs

Cf. A000203, A211656, A211657, A211658, A211660.

Sequence in context: A015840 A051213 A340111 * A301806 A374057 A066847

Adjacent sequences: A211656 A211657 A211658 * A211660 A211661 A211662

Keyword

nonn

Author

Jaroslav Krizek, Apr 20 2012

Status

approved