A145172 Number of pentagonal numbers needed to represent n with greedy algorithm.

1, 2, 3, 4, 1, 2, 3, 4, 5, 2, 3, 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 2, 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 2, 3, 4, 5, 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 2, 3, 4, 5, 6, 3, 4, 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 2, 3, 4, 5, 6, 3, 4, 5, 6

Offset: 1

Author

Christina Steffan (christina.steffan(AT)gmx.at), Oct 03 2008

Keywords

• nonn

Comments

Sequence is unbounded.

Examples

			a(21)=6 since 21 = 12+5+1+1+1+1.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000326 (pentagonal numbers), A053610, A057945, A180447, A192988.

Programs

PARI

a(n)={my(s=0); forstep(k=(sqrtint(24*n+1)+1)\6, 1, -1, my(t=k*(3*k-1)/2); s+=n\t; n%=t); s} \\ Andrew Howroyd, Apr 21 2021

Extensions

Terms a(41) and beyond from Andrew Howroyd, Apr 21 2021