A063700 Numbers k such that sigma(k + d(k)) = sigma(k) + d(k), where sigma() = A000203(), d() = A000005().

3, 5, 11, 17, 29, 41, 59, 71, 101, 107, 137, 147, 149, 179, 191, 197, 227, 239, 269, 281, 311, 347, 419, 431, 461, 521, 569, 596, 599, 617, 641, 659, 809, 821, 827, 857, 881, 1019, 1031, 1049, 1061, 1091, 1151, 1229, 1277, 1289, 1301, 1319, 1427, 1451, 1481

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

Primes and composites among solutions:
k = 59, d(59) = 2, sigma(59) = 60, sigma(59+2) = sigma(61) = 62 = sigma(59) + d(59);
k = 596, d(596) = 6, sigma(596) = 1050, sigma(596+6) = sigma(602) = 1056 = sigma(596) + d(596).

Prog

(PARI) { n=0; for (x=1, 10^9, if (sigma(x + numdiv(x)) == (sigma(x) + numdiv(x)), write("b063700.txt", n++, " ", x); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 28 2009

Crossrefs

Cf. A000005, A000203.

Sequence in context: A141262 A069233 A329946 * A078859 A054799 A093326

Adjacent sequences: A063697 A063698 A063699 * A063701 A063702 A063703

Keyword

nonn

Author

Labos Elemer, Aug 23 2001

Status

approved