A112665 Numbers that cannot be expressed as a sum of 2 triangular numbers and a power of 2.

6222, 18081, 22161, 23428, 27342, 29847, 36115, 44137, 47677, 50211, 52534, 56751, 57220, 64008, 70146, 78210, 79632, 81003, 82396, 83538, 84531, 85603, 92374, 92847, 96441, 96873, 97054, 97461, 103572, 103935, 109045, 119685, 121134

Offset

1,1

Comments

Sequence proposed by Livio Zucca on it.hobby.enigmi. First prime number appearing is 152539. (Cf. A112625)

Links

Table of n, a(n) for n=1..33.

Example

6221 and 6223 are not in the sequence since they can be expressed as 6221 = T(105) + T(32) + 2^7 and 6223 = T(93) + T(56) + 2^8.

Mathematica

tab = Table[1, {i, 30000}]; T[n_] := (n + n^2)/2; Do[n=T[i]+T[j]+2^k; If[1<=n<=30000, tab[[n]]=0], {i, 0, 244}, {j, 0, i}, {k, 0, 14}]; Position[tab, 1] // Flatten

Crossrefs

Cf. A112625.

Sequence in context: A330364 A230733 A293355 * A330933 A232390 A092726

Adjacent sequences: A112662 A112663 A112664 * A112666 A112667 A112668

Keyword

nonn

Author

Giovanni Resta, Jan 12 2006

Status

approved