A115706 Primes whose digit reversal is a pentagonal number (A000326).

5, 29, 53, 541, 673, 2239, 5273, 6257, 7753, 10567, 10861, 10883, 15137, 27793, 28447, 28723, 29201, 52639, 54001, 56041, 59863, 62143, 67189, 67349, 74587, 76771, 103591, 103811, 104971, 108643, 157637, 212161, 217223, 229343, 241391

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..250

Example

541 is prime and 145 is the 10th pentagonal number.

Mathematica

Select[Prime[Range[22000]], IntegerQ[(1+Sqrt[1+24*IntegerReverse[#]])/6]&] (* Harvey P. Dale, Jan 25 2026 *)

Crossrefs

Cf. A000326, A115707.

Sequence in context: A147153 A300777 A177831 * A031394 A103094 A341083

Adjacent sequences: A115703 A115704 A115705 * A115707 A115708 A115709

Keyword

nonn,base

Author

Giovanni Resta, Jan 31 2006

Status

approved