A050679 Positions of 2's in A048288.

2, 3, 4, 6, 7, 11

Offset: 1

Author

Patrick De Geest, Aug 15 1999

Keywords

• nonn
• base
• hard
• more

Links

• Patrick De Geest, Reversed Smarandache Concatenated Numbers, Prime factors from n down to 1
• M. Fleuren, Factors and primes of Smarandache sequences.
• M. Fleuren, Smarandache Factors and Reverse factors
• Carlos Rivera, Puzzle 8. Primes by Listing, The Prime Puzzles & Problems connection.

Crossrefs

Cf. A000422, A046461, A048288, A050680, A050681, A050682.

Programs

Mathematica

Select[Range[2,12],PrimeOmega[FromDigits[Flatten[IntegerDigits[Range[#,1,-1]]]]]==2 &] (* Jayanta Basu, May 30 2013 *)

Extensions

Offset changed to 1 by Jinyuan Wang, Sep 04 2021