A212532 Number of nondecreasing sequences of n 1..4 integers with every element dividing the sequence sum.
4, 4, 7, 10, 15, 15, 24, 29, 39, 45, 57, 65, 83, 92, 111, 127, 149, 163, 193, 213, 245, 270, 305, 333, 378, 408, 455, 496, 547, 587, 650, 697, 763, 819, 889, 949, 1033, 1096, 1183, 1261, 1353, 1431, 1539, 1625, 1737, 1836, 1953, 2057, 2192, 2300, 2439, 2566, 2711
Offset: 1
Keywords
Examples
Some solutions for n=8: ..1....4....2....2....1....1....1....2....1....1....1....2....3....1....1....1 ..1....4....2....3....1....1....1....2....1....2....1....2....3....1....1....3 ..2....4....2....3....1....2....1....4....1....2....3....2....3....1....2....3 ..4....4....2....3....3....2....1....4....1....2....3....2....3....1....2....3 ..4....4....4....3....3....2....1....4....1....2....4....2....3....1....2....3 ..4....4....4....3....3....2....1....4....1....3....4....2....3....1....4....3 ..4....4....4....3....3....2....2....4....2....3....4....4....3....3....4....4 ..4....4....4....4....3....4....2....4....4....3....4....4....3....3....4....4
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A212536.
Formula
Empirical: a(n) = a(n-1) + a(n-2) - a(n-4) - a(n-5) + a(n-6) + a(n-12) - a(n-13) - a(n-14) + a(n-16) + a(n-17) - a(n-18).
Empirical g.f.: x*(4 - x^2 - x^3 + 2*x^4 - 2*x^5 + x^6 + 3*x^7 + 4*x^8 - 3*x^9 - 3*x^10 + x^11 + x^12 - x^13 + 2*x^15 - x^17) / ((1 - x)^4*(1 + x)^2*(1 - x + x^2)*(1 + x^2)*(1 + x + x^2)^2*(1 - x^2 + x^4)). - Colin Barker, Jul 20 2018
Comments