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Search: id:A088604
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| A088604 |
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a(n) = smallest prime in which n substrings containing the least significant digit are primes. |
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+0
3
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| 2, 13, 113, 1223, 12113, 121283, 1237547, 12184967, 124536947, 1219861613, 12181833347, 121339693967, 1213536676883, 12673876537547, 121848768729173, 1275463876537547, 12429121339693967, 165678739293946997
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n) need not contain a(n-1) as a substring.
We exclude substrings that begin with 0, so a(3) is not 103. - David Wasserman (wasserma(AT)spawar.navy.mil), Aug 12 2005
Agrees with A127891 for 24 terms, but A127891 ends there while this sequence continues. - Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 13 2007
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EXAMPLE
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a(4) = 1223 in which the four substrings containing the LSD (3,23,223,1223) are primes.
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PROGRAM
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(PARI) f(n, d, digs, spare) = local(p, r, found); if (!d, return(n)); found = 0; for (i = 0, 9, p = n + i*10^digs; if ((i && isprime(p)) || spare, r = f(p, d - 1, digs + 1, spare - 1 + (i && isprime(p)))); if (r && (r < found || !found), found = r)); found; a(n) = local(i, r); i = 0; while (1, r = f(0, n + i, 0, i); if (r, return(r), i++)); (Wasserman)
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CROSSREFS
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Cf. A088603, A127891.
Adjacent sequences: A088601 A088602 A088603 this_sequence A088605 A088606 A088607
Sequence in context: A046811 A046813 A096497 this_sequence A127891 A110369 A000180
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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), Oct 15 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Aug 12 2005
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