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.

A179826 Primes that can be obtained from composite numbers by interchanging the first and last digits.

This page as a plain text file.
%I A179826 #9 Jul 16 2022 11:58:43
%S A179826 41,61,2,3,23,43,53,83,5,7,47,67,19,29,59,89,401,601,11,211,811,911,
%T A179826 421,521,821,31,331,431,631,41,241,541,641,251,61,461,661,71,271,571,
%U A179826 281,881,491,691,2,3,103,503,13,613,23,223,523,823,233,433,43,443,643,53
%N A179826 Primes that can be obtained from composite numbers by interchanging the first and last digits.
%C A179826 The composite number must contain at least two digits.
%C A179826 Primes may be repeated; the reverted A002808(j) are investigated along increasing j and their trailing zeros become leading zeros and are dropped. [_R. J. Mathar_, Jul 30 2010]
%e A179826 41 is a prime from the composite number 14 by interchanging the first and last digit. 47 is a prime from the composite number 74 by interchanging the first and last digit.
%t A179826 nonpr=Complement[Range[10,1000],Prime[Range[PrimePi[1000]]]];
%t A179826 swtch[n_]:=Module[{idn=IntegerDigits[n],f,l,m},f=First[idn];l=Last[idn];m=Most[Rest[idn]];FromDigits[Join[{l},m,{f}]]]
%t A179826 Select[swtch[#]&/@nonpr,PrimeQ] (* _Harvey P. Dale_, Dec 14 2010 *)
%K A179826 base,nonn
%O A179826 1,1
%A A179826 _Parthasarathy Nambi_, Jul 29 2010
%E A179826 Minor edits by _N. J. A. Sloane_, Jul 29 2010
%E A179826 More terms from _R. J. Mathar_, Jul 30 2010