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Search: id:A072348
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| A072348 |
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Number of primes whose decimal representation has the form rns where r and s are single digits. |
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+0
1
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| 15, 13, 13, 15, 14, 16, 15, 15, 13, 14, 11, 10, 12, 9, 5, 12, 10, 10, 8, 8, 12, 13, 13, 13, 9, 11, 8, 12, 12, 13, 11, 10, 11, 10, 11, 9, 9, 11, 10, 12, 5, 11, 11, 12, 12, 11, 12, 10, 11, 9, 7, 10, 14, 11, 14, 11, 9, 10, 10, 11, 11, 8, 12, 10, 12, 12, 11, 13, 11, 15, 11, 11, 10, 12
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(2437) = 0 and a(n)>0 for n<2437, see A069691(2437) = 0;
a(1660) = 1 and a(n)>1 for n<1660, A069691(1660) = 216607;
a(n) <= 16 for all n, a(5) = 16, conjecture: a(n)<16 for n>5.
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EXAMPLE
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The 16 prime sandwiches for n=5: 151, 157, 251, 257, 353, 359, 457, 557, 653, 659, 751, 757, 853, 857, 859 and 953.
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CROSSREFS
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Sequence in context: A013430 A131082 A097953 this_sequence A129786 A104056 A131285
Adjacent sequences: A072345 A072346 A072347 this_sequence A072349 A072350 A072351
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KEYWORD
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nonn,base
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 17 2002
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