The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A330861 Number of ways to represent n as a sum of 2 triangular numbers and a perfect square. 2
 1, 2, 2, 2, 3, 2, 3, 4, 2, 2, 5, 4, 3, 4, 2, 4, 6, 4, 3, 4, 5, 4, 7, 2, 3, 8, 4, 4, 5, 6, 4, 8, 6, 2, 5, 4, 6, 8, 7, 4, 8, 4, 5, 8, 2, 6, 10, 8, 3, 6, 6, 6, 10, 4, 4, 10, 8, 6, 7, 6, 7, 8, 6, 2, 9, 10, 6, 12, 4, 4, 11, 8, 6, 10, 8, 4, 10, 6, 5, 6, 10, 10, 12, 6, 5, 14, 4, 8, 9, 4, 6, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The range of the two triangular numbers and the square is the non-negative numbers. LINKS EXAMPLE a(0)=1 because there is one representation 0 = T(0)+T(0)+0^2. a(1)=2 because there are 2 representations 1 = T(0)+T(0)+1^2 = T(0)+T(1)+0^2. a(4)=3 because there are 3 representations 4 = T(0)+T(0)+2^2 = T(0)+T(2)+1^2 = T(1)+T(2)+0^2. MAPLE A330861 := proc(n)     local a, t1idx, t2idx, t1, t2;     a := 0 ;     for t1idx from 0 do         t1 := A000217(t1idx) ;         if t1 > n then             break;         end if;         for t2idx from t1idx do             t2 := A000217(t2idx) ;             if t1+t2 > n then                 break;             end if;             if issqr(n-t1-t2) then                 a := a+1 ;             end if;         end do:     end do:     a ; end proc: CROSSREFS Cf. A115288 (greedy inverse). Sequence in context: A194344 A128435 A220415 * A286565 A219354 A026903 Adjacent sequences:  A330858 A330859 A330860 * A330862 A330863 A330864 KEYWORD nonn AUTHOR R. J. Mathar, Apr 28 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 9 18:32 EDT 2020. Contains 336326 sequences. (Running on oeis4.)