A212864 Number of nondecreasing sequences of n 1..4 integers with no element dividing the sequence sum.
0, 2, 3, 5, 6, 9, 12, 15, 17, 22, 26, 30, 34, 40, 45, 51, 56, 63, 70, 77, 83, 92, 100, 108, 116, 126, 135, 145, 154, 165, 176, 187, 197, 210, 222, 234, 246, 260, 273, 287, 300, 315, 330, 345, 359, 376, 392, 408, 424, 442, 459, 477, 494, 513, 532, 551, 569, 590, 610, 630, 650
Offset: 1
Keywords
Examples
All solutions for n=8: ..2....2....2....2....2....2....3....2....2....3....2....2....2....3....3 ..2....3....2....2....2....2....3....2....3....3....2....3....2....4....3 ..3....3....2....2....2....2....3....3....4....3....2....3....2....4....3 ..3....3....2....2....2....2....3....3....4....3....3....3....3....4....4 ..3....3....3....2....2....2....3....3....4....3....4....3....3....4....4 ..3....3....4....2....2....3....3....4....4....3....4....3....3....4....4 ..3....3....4....3....2....3....4....4....4....3....4....4....4....4....4 ..4....3....4....4....3....3....4....4....4....4....4....4....4....4....4
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A212868.
Formula
Empirical: a(n) = a(n-1) + a(n-3) - a(n-5) - a(n-7) + a(n-8).
Empirical g.f.: x^2*(2 + x + 2*x^2 - x^3) / ((1 - x)^3*(1 + x)*(1 + x^2)*(1 + x + x^2)). - Colin Barker, Jul 21 2018
Comments