A185253 a(n) = A185128(n) - A185129(n).

6, 66, 325, 210, 1596, 2701, 1326, 903, 1225, 16836, 6903, 82621, 141778, 181503, 63546, 52975, 354903, 10440, 13530, 405450, 7140, 989121, 1329265, 511566, 668746, 437580, 2102275, 2001000, 2469753, 3229611, 1428895, 3096316, 1963171, 6843150, 856086, 4276350

Offset

1,1

References

Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966, p. 197, no. 8.

Links

Table of n, a(n) for n=1..36.

N. J. A. Sloane, Annotated scan of Beiler's Table 81, based on page 197 of Beiler's "Recreations in the Theory of Numbers: The Queen of Mathematics Entertains", New York, Dover, First ed., 1964.

Mathematica

kmax=2000; TriangularQ[n_]:=IntegerQ[(Sqrt[1+8n]-1)/2]; A000217[n_]:=n(n+1)/2; a={}; For[k=1, k<=kmax, k++, For[h=1, A000217[h]<A000217[k], h++, If[TriangularQ[d=A000217[k] - A000217[h]] && TriangularQ[A000217[k]+A000217[h]], AppendTo[a, d]]]]; a (* Stefano Spezia, Sep 02 2024 *)

Prog

(PARI) lista(nn) = {v = vector(nn, n, n*(n+1)/2); for (n=2, nn, for (k=1, n-1, if (ispolygonal(v[n]+v[k], 3) && ispolygonal(v[n]-v[k], 3), print1(v[n]-v[k], ", ")); ); ); } \\ Michel Marcus, Jan 08 2015

Crossrefs

Cf. A000217, A185128, A185129, A185223, A185233, A185243, A185257, A185258.

Sequence in context: A119172 A064167 A175455 * A192089 A119073 A028559

Adjacent sequences: A185250 A185251 A185252 * A185254 A185255 A185256

Keyword

nonn

Author

Martin Renner, Jan 20 2012

Extensions

Edited by N. J. A. Sloane, Dec 28 2024 (replaced definition with simpler and more explicit formula from Michel Marcus, Jan 08 2015)

Status

approved