A115677 Brilliant numbers (A078972) whose digit reversal is a triangular number.

6, 10, 649, 1207, 54253, 56341, 60391, 66259, 66331, 101971, 155143, 166339, 351433, 672319, 3003193, 3054853, 5043763, 5631229, 5858119, 6163831, 6256603, 6462847, 6473899, 6556177, 6687883, 8210989, 8236513, 8735491, 8788033, 10716571, 11576143

Offset

1,1

Links

Table of n, a(n) for n=1..31.

Example

649=11*59 is brilliant and 946=T(43).

Mathematica

bnoQ[n_]:=Module[{fi=FactorInteger[n], tfi, nn}, tfi=Transpose[fi]; Total[tfi[[2]]]==2 &&IntegerLength[First[tfi[[1]]]] == IntegerLength[Last[tfi[[1]]]]]; tnoQ[n_]:=IntegerQ[(Sqrt[1 +8FromDigits[ Reverse[IntegerDigits[n]]]]-1)/2]; Select[Select[Range[700000], bnoQ], tnoQ]  (* Harvey P. Dale, Apr 17 2011 *)

Crossrefs

Cf. A078972, A115678.

Sequence in context: A153022 A262081 A268537 * A284738 A100129 A009443

Adjacent sequences: A115674 A115675 A115676 * A115678 A115679 A115680

Keyword

nonn,base

Author

Giovanni Resta, Jan 31 2006

Extensions

a(15)-a(31) from Donovan Johnson, Apr 26 2011

Status

approved