A048525 Primes for which only three iterations of 'Prime plus its digit sum equals a prime' are possible.

277, 1559, 5779, 7489, 11279, 15091, 22093, 37811, 43579, 46279, 48541, 49957, 53479, 54751, 60589, 68473, 72883, 74821, 83621, 85621, 90793, 91921, 93901, 97501, 107981, 110899, 111799, 120193, 153379, 157739, 170299, 180731, 184441

Offset

1,1

Links

Lars Blomberg, Table of n, a(n) for n = 1..10000

Example

prime 7489 -> 7489 + (7+4+8+9) = prime 7517 -> 7517 + (7+5+1+7) = prime 7537 -> 7537 + (7+5+3+7) = prime 7559 -> next iteration yields composite 7585.

Mathematica

tiQ[p_]:=Boole[PrimeQ[NestList[#+Total[IntegerDigits[#]]&, p, 4]]]=={1, 1, 1, 1, 0}; Select[Prime[Range[20000]], tiQ] (* Harvey P. Dale, Dec 02 2024 *)

Crossrefs

Cf. A047791, A048519.

Sequence in context: A105977 A297891 A236803 * A189609 A264371 A154231

Adjacent sequences: A048522 A048523 A048524 * A048526 A048527 A048528

Keyword

nonn,base

Author

Patrick De Geest, May 15 1999

Status

approved