A111462 a(1) = 7, then smallest prime beginning with the digit reversal of the previous term.

7, 71, 17, 719, 9173, 3719, 91733, 3371947, 7491733, 33719479, 974917337, 73371947923, 3297491733763, 367337194792327, 72329749173376301, 1036733719479232777, 777232974917337630173, 37103673371947923277727

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Example

a(3) = 17 because a(2) = 71 and the digit reversal of 71 is 17 which is prime
a(4) = 719 because a(3) = 17, digit reversal of 17 is 71 which is already in the list. Smallest prime that starts with 71 is 719.

Maple

reverse := proc (nn) local n, m; m := 0; n := nn; while (n > 0) do m := m*10 + irem(n, 10, 'n'); od; m; end:
a := proc(n, m) option remember; global currSet; local currN, i, origN, j; if n = 0 then currSet := {m}; return m; end if; currN := reverse(a(n - 1, m)); if (not (evalb(currN in currSet))) then if (isprime(currN)) then currSet := currSet union {currN}; return currN; end if; end if; origN := currN; j := 1; while (true) do origN := 10 * origN; currN := origN; i := 0; while i < (10^j) do if (isprime(currN) and (not evalb(currN in currSet))) then currSet := currSet union {currN}; return currN; end if; currN := currN + 1; i := i + 1; end do; j := j + 1; end do; return currN; end proc; (Delgau)

Crossrefs

Cf. A111463, A090543.

Sequence in context: A097630 A090647 A200929 * A045713 A090155 A326740

Adjacent sequences: A111459 A111460 A111461 * A111463 A111464 A111465

Keyword

base,nonn

Author

Amarnath Murthy, Aug 04 2005

Extensions

More terms from Chris Deugau (deugaucj(AT)uvic.ca), Nov 07 2005

Status

approved