A180436 Palindromic numbers which are sum of consecutive squares.

1, 4, 5, 9, 55, 77, 121, 181, 313, 434, 484, 505, 545, 595, 636, 676, 818, 1001, 1111, 1441, 1771, 4334, 6446, 10201, 12321, 14641, 17371, 17871, 19691, 21712, 40804, 41214, 42924, 44444, 44944, 46564, 51015, 65756, 69696, 81818, 94249, 97679, 99199

Offset

1,2

Comments

In more than one way: 554455, 9343439, ... (A267600) - Robert G. Wilson v, May 28 2012

Links

Giovanni Resta, Table of n, a(n) for n = 1..10400 (terms < 10^18, first 228 terms from Robert G. Wilson v)

Example

1001 is in the sequence because 1001 is palindromic and it can be written as sum of consecutive squares (1001 = 4^2 + 5^2 + 6^2 + ... + 13^2 + 14^2).

Mathematica

palQ[n_Integer] := Block[{idn = IntegerDigits[n]}, idn == Reverse[idn]]; lst = {}; k = 1; While[k < 1000, AppendTo[lst, Select[ Accumulate[ Range[k, 1000]^2], palQ]]; lst = Union@ Flatten@ lst; k++]; Select[lst, # < 10^6 &] (* Robert G. Wilson v, May 28 2012 *)

Crossrefs

Cf. A002113, A002779, A034705, A216446, A267600.

Sequence in context: A041151 A279919 A041467 * A121919 A041627 A132811

Adjacent sequences: A180433 A180434 A180435 * A180437 A180438 A180439

Keyword

nonn,easy,base

Author

Zhining Yang, Jan 19 2011

Status

approved