A134189 a(1)=1. Thereafter, a(n) = n*a(n-1) if the number of divisors of n*a(n-1) is <= the number of divisors of n+a(n-1) or a(n) = n+a(n-1) if n*a(n-1) has more divisors than n+a(n-1).

1, 2, 5, 9, 14, 20, 27, 35, 44, 54, 65, 77, 1001, 1015, 1030, 1046, 1063, 1081, 20539, 20559, 431739, 431761, 9930503, 9930527, 248263175, 248263201, 248263228, 248263256, 248263285, 248263315, 248263346, 248263378, 248263411, 8440955974, 8440956009

Offset

1,2

Links

Table of n, a(n) for n=1..35.

Example

a(12)+13 = 77 + 13 = 90. a(12)*13 = 77 * 13 = 1001. 90 has 12 divisors. 1001 has 8 divisors. Since 1001 has fewer divisors than 90, a(13) is 1001.

Prog

(PARI) lista(nn) = {preca = 1; print1(preca, ", "); for (i = 2, nn, if (numdiv(p=i*preca) <= numdiv(s=i+preca), nexta = p, nexta = s); print1(nexta, ", "); preca = nexta; ); } \\ Michel Marcus, Feb 10 2014

Crossrefs

Cf. A134190.

Sequence in context: A080956 A132337 A000096 * A109470 A112873 A048093

Adjacent sequences: A134186 A134187 A134188 * A134190 A134191 A134192

Keyword

nonn

Author

Leroy Quet, Oct 12 2007

Extensions

More terms from Michel Marcus, Feb 10 2014

Status

approved