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 A082622 a(1) = 3, a(n) = smallest palindromic prime obtained by inserting two paired digits anywhere in a(n-1). 6
 3, 131, 10301, 1003001, 100030001, 10070307001, 1000703070001, 100075030570001, 10006750305760001, 1000167503057610001, 100015675030576510001, 10001056750305765010001, 1000105367503057635010001, 100001053675030576350100001, 10000105360750305706350100001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS With the exception of 11, all decimal palindromic numbers with an even number of digits are composite (they are divisible by 11). This leaves only odd-digit-length palindromes, therefore (at least) a pair of digits needs to be inserted at every iteration. The sequence terminates at a(19) = 1000010025136075033305706315200100001, which cannot be extended to another palindromic prime by inserting two paired digits. - Giovanni Resta, Sep 20 2019 LINKS Giovanni Resta, Table of n, a(n) for n = 1..19 PROG (PARI) \\ Warning: program gives incorrect results; Michel Marcus, Sep 21 2019 {w=[]; print(1" "3); for(i=2, 58, w=concat(0, w); for(pos=1, i, if(pos>1, w[pos-1]=w[pos]); for(d=0, 9, w[pos]=d; if(isprime(n=fromdigits(concat(Vecrev(w), concat(3, w)))), print(i" "n); break(2)))))} \\ Serge Batalov, Dec 18 2015 CROSSREFS Cf. A082620, A082621. Sequence in context: A005175 A347985 A082439 * A332113 A075597 A262639 Adjacent sequences:  A082619 A082620 A082621 * A082623 A082624 A082625 KEYWORD nonn,base,fini,full AUTHOR Amarnath Murthy, Apr 29 2003 EXTENSIONS a(6)-a(56) from Serge Batalov, Dec 18 2015 Terms following a(6) corrected by Giovanni Resta, Sep 20 2019 STATUS approved

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Last modified January 27 22:22 EST 2022. Contains 350654 sequences. (Running on oeis4.)