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A032437 Substrings from the right are prime numbers (using only odd digits different from 5).

%I A032437 #33 Feb 16 2025 08:32:36
%S A032437 3,7,13,17,37,73,97,113,137,173,197,313,317,337,373,397,773,797,937,
%T A032437 997,1373,1997,3137,3313,3373,3797,7937,9137,9173,9337,9397,13313,
%U A032437 33797,39397,79337,79397,91373,91997,99137,99173,99397,139397,379397
%N A032437 Substrings from the right are prime numbers (using only odd digits different from 5).
%C A032437 Primes p with decimal expansion d_1 d_2 d_3 ... d_k such that the digits d_i are 1, 3, 7, or 9, and deleting 1, 2, 3, up to k-1 leading digits also produces a prime. For example, 9173 is a term because all of 9173, 173, 73, and 3 are primes. - _N. J. A. Sloane_, Jun 28 2022
%H A032437 T. D. Noe, <a href="/A032437/b032437.txt">Table of n, a(n) for n = 1..58</a> [The complete list of terms]
%H A032437 C. Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_002.htm">Prime strings</a>
%H A032437 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TruncatablePrime.html">Truncatable Prime.</a>
%e A032437 173 is a term because 173, 73, and 3 are all primes. 371 is not a term because 371 and 1 are not primes. - _N. J. A. Sloane_, Jun 28 2022
%t A032437 Select[Prime[Range[33000]],SubsetQ[{1,3,7,9},IntegerDigits[#]]&&AllTrue[Mod[#,10^Range[ IntegerLength[ #]-1]],PrimeQ]&] (* _Harvey P. Dale_, Jun 28 2022 *)
%o A032437 (PARI) is(n)=my(d=digits(n)); for(i=1,n, if(!isprime(fromdigits(d[i..n])), return(0))); 1 \\ _Charles R Greathouse IV_, Jun 25 2017
%Y A032437 Cf. A033664, A024785, A020994, A024770, A052023, A052024, A052025, A050986, A050987.
%K A032437 nonn,fini,full,base,nice
%O A032437 1,1
%A A032437 _Carlos Rivera_
%E A032437 Single-digit terms added by _Eric W. Weisstein_.