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A077390
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Primes which leave primes at every step if most significant digit and least significant digit are deleted until a one digit or two digit prime is obtained.
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5
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2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 127, 131, 137, 139, 151, 157, 173, 179, 223, 227, 229, 233, 239, 251, 257, 271, 277, 331, 337, 353, 359, 373, 379, 421, 431, 433, 439, 457, 479, 521, 523, 557, 571, 577, 631, 653, 659
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| There are exactly 920720315 such primes, the largest being 9161759674286961988443272139114537477768682563429152377117139 1111313737919133977331737137933773713713973. - Karl W. Heuer, Apr 19 2011
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LINKS
| T. D. Noe, Table of n, a(n) for n = 1..12975
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EXAMPLE
| 21313 is a member as 21313, 131 and 3 all are primes.
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MATHEMATICA
| msd={1, 2, 3, 4, 5, 6, 7, 8, 9}; lsd={1, 3, 7, 9}; Clear[p]; p[1]={2, 3, 5, 7}; p[2]={11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97}; p[digits_] := p[digits] = Select[Flatten[Outer[Plus, 10^(digits-1)*msd, 10*p[digits-2], lsd]], PrimeQ]; t={}; k=0; While[Length[t] < 100, k++; t=Join[t, p[k]]]; t (* T. D. Noe, Apr 19 2011 *)
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CROSSREFS
| cf. A024770 (left-truncatable primes), A024785 (right-truncatable primes), A137812 (left-or-right truncatable primes).
Sequence in context: A030475 A069676 A062353 * A069677 A069678 A069679
Adjacent sequences: A077387 A077388 A077389 * A077391 A077392 A077393
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KEYWORD
| base,fini,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 07 2002
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EXTENSIONS
| Corrected and extended by T. D. Noe (noe(AT)sspectra.com), Apr 19 2011
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