A235203 Positive integers not represented by xyzw + xy + yz + zw + wx when evaluated over the positive integers.

1, 2, 3, 4, 6, 7, 9, 10, 15, 19, 22, 30, 37, 42, 57, 70, 79, 187, 190, 274, 715, 1317

Offset

1,2

Comments

No other terms < 10^8. Sequence is probably finite. - Giovanni Resta, Jan 04 2014

Links

Table of n, a(n) for n=1..22.

Maple

f := proc (x, y, z, w) x*y*z*w+x*y+y*z+z*w+w*x end proc: N := 1500: S := {}: for i to floor(N^(1/4)) do for j to floor((N/i)^(1/3)) do for k to floor((N/(i*j))^(1/2)) do for l to floor(N/(i*j*k)) do S := {f(i, j, k, l), f(i, j, l, k), f(i, k, j, l), op(S)} end do end do end do end do: `minus`({seq(i, i = 1 .. N)}, S);
#Note: f is invariant under a dihedral permutation of (x, y, z, w); the above program finds elements of the sequence with choice of upper bound N = 1500

Crossrefs

Sequence in context: A076679 A339509 A060233 * A187102 A191991 A369138

Adjacent sequences: A235200 A235201 A235202 * A235204 A235205 A235206

Keyword

nonn

Author

C. Carroll, Jan 04 2014

Status

approved