A176873 Smallest possible integer m>=3 such that n is the sum of an m-gonal number and a k-gonal number for some k<=m.

3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 4, 3, 3, 3, 5, 3, 3, 4, 3, 3, 3, 3, 3, 4, 5, 3, 4, 3, 3, 3, 3, 4, 4, 3, 3, 4, 3, 3, 5, 3, 3, 4, 3, 4, 4, 4, 3, 3, 3, 3, 4, 3, 3, 7, 5, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 4, 4, 3, 4, 3, 3, 4, 3, 4, 3, 3, 4, 5, 3, 3, 4, 3, 3, 3, 3, 3, 4, 4, 3, 4, 3, 3, 3, 3, 4, 4

Offset

0,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 0..10000

Formula

a(n) = min max(A176774(i),A176774(n-i)), where min is taken over i=0,1,...,n under the assumption that A176774(2) = +infinity.

Prog

(PARI) a(n)=if(ispolygonal(n, 3) || ispolygonal(n-1, 3), return(3)); for(m=3, if(n>5, (n+1)\2, 4), my(i=2, t); while((t=n-(m-2)*binomial(i, 2)-i)>=0, for(k=3, m, if(ispolygonal(t, k), return(m))); i++)) \\ Charles R Greathouse IV, Dec 11 2015

Crossrefs

Cf. A176774, A176874.

Sequence in context: A209291 A375642 A332875 * A227727 A050499 A304431

Adjacent sequences: A176870 A176871 A176872 * A176874 A176875 A176876

Keyword

nonn

Author

Max Alekseyev, Apr 27 2010

Status

approved