A026468 a(1) = 1, a(2) = 2; for n >= 3, a(n) = least positive integer > a(n-1) and not a(i)^2 + a(j)^2 for 1<=i<=j<=n-1.

1, 2, 3, 4, 6, 7, 9, 11, 12, 14, 15, 16, 19, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 38, 39, 41, 42, 43, 44, 46, 47, 48, 49, 51, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78

Offset

1,2

Links

Table of n, a(n) for n=1..60.

Maple

# return true if 'candid' is allowed (not a sum of squares)
A026469aux := proc(a, candid) local i, j; for j from 1 to nops(a) do for i from 1 to j do if (op(i, a))^2+(op(j, a))^2 = candid then RETURN(false); fi; od; od; RETURN(true); end:
A026468 := proc(nmax) local a, candidat; a := [1, 2]; while nops(a) < nmax do candidat := op(nops(a), a)+1; while A026469aux(a, candidat) = false do candidat := candidat+1; od; a := [op(a), candidat]; od: RETURN(a); end: A026468(60); # R. J. Mathar, Nov 01 2006

Crossrefs

A022544 is a subsequence.

Cf. A026469, A261604.

Sequence in context: A369138 A257047 A192416 * A263015 A056176 A143831

Adjacent sequences: A026465 A026466 A026467 * A026469 A026470 A026471

Keyword

nonn

Author

Clark Kimberling

Extensions

Definition corrected by Ralf Stephan, Nov 01 2006

Status

approved