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

1,2

Comments

Sequence is unbounded.

Links

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

Example

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

Prog

(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

Crossrefs

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

Sequence in context: A053344 A092196 A100878 * A338484 A338493 A280053

Adjacent sequences: A145169 A145170 A145171 * A145173 A145174 A145175

Keyword

nonn

Author

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

Extensions

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

Status

approved