A072387 Triangular number x such that x + reverse of x is a prime.

1, 10, 190, 11026, 11476, 12880, 13366, 19306, 21115, 23005, 26335, 28441, 36046, 53956, 54946, 58996, 60031, 65341, 68635, 70876, 72010, 83845, 91378, 1030330, 1047628, 1095940, 1100386, 1154440, 1205128, 1209790, 1223830, 1242676, 1247410, 1266436, 1285606

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

10 is a term because it is a triangular number and 10 + 01 = 11 is a prime.

Mathematica

tri[n_] := n*(n + 1)/2; tri /@ Select[Range[10^3], PrimeQ[(t = tri[#]) + FromDigits @ Reverse @ IntegerDigits[t]] &] (* Amiram Eldar, Aug 24 2020 *)
Select[Accumulate[Range[2000]], PrimeQ[#+IntegerReverse[#]]&] (* Harvey P. Dale, Nov 27 2021 *)

Prog

(PARI) isok(n) = ispolygonal(n, 3) && isprime(n+subst(Polrev(digits(n)), x, 10)); \\ Michel Marcus, Nov 29 2014

Crossrefs

Intersection of A000217 and A072366. - Michel Marcus, Nov 29 2014

Cf. A056964.

Sequence in context: A211826 A144772 A045756 * A356495 A244385 A134633

Adjacent sequences: A072384 A072385 A072386 * A072388 A072389 A072390

Keyword

base,nonn

Author

Shyam Sunder Gupta, Jul 20 2002

Extensions

More terms from Michel Marcus, Nov 29 2014

Status

approved