cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A070029 Primes with only prime digits and whose initial, all intermediate and final iterated sums of digits are primes.

Original entry on oeis.org

2, 3, 5, 7, 23, 223, 227, 353, 2333, 2777, 3323, 7727, 27527, 33377, 33773, 35537, 35573, 35753, 37337, 52727, 53777, 55337, 55373, 55733, 57557, 57737, 57773, 73553, 73757, 75227, 75353, 75377, 75533, 75557, 75773, 77573, 222557, 222773
Offset: 1

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Author

Rick L. Shepherd, Apr 21 2002

Keywords

Comments

This sequence is the intersection of A062088 and A070027.

Examples

			53777 is a term because 53777 is a prime with only prime digits and 5+3+7+7+7=29, 2+9=11 and 1+1=2 are all prime.
		

Crossrefs

Cf. A070027, A062088 (only first sum of digits is necessarily prime).

Programs

  • Mathematica
    iifpQ[n_]:=AllTrue[NestWhileList[Total[IntegerDigits[#]]&,n,#>9&],PrimeQ]; Select[Prime[Range[20000]],AllTrue[IntegerDigits[#],PrimeQ]&&iifpQ[#]&] (* Harvey P. Dale, Jul 18 2021 *)