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Search: id:A111462
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| A111462 |
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a(1) = 7, then smallest prime beginning with the digit reversal of the previous term. |
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+0
3
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| 7, 71, 17, 719, 9173, 3719, 91733, 3371947, 7491733, 33719479, 974917337, 73371947923, 3297491733763, 367337194792327, 72329749173376301, 1036733719479232777, 777232974917337630173, 37103673371947923277727
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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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.
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MAPLE
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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)
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CROSSREFS
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Cf. A111463, A090543.
Sequence in context: A051604 A097630 A090647 this_sequence A045713 A090155 A107163
Adjacent sequences: A111459 A111460 A111461 this_sequence A111463 A111464 A111465
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 04 2005
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EXTENSIONS
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More terms from Chris Deugau (deugaucj(AT)uvic.ca), Nov 07 2005
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