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Search: id:A076497
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| A076497 |
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Number of primes corresponding to n-th primeval number A072857(n). |
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+0
4
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| 0, 1, 3, 4, 5, 7, 11, 14, 19, 21, 26, 29, 31, 33, 35, 41, 53, 55, 60, 64, 89, 96, 106, 122, 153, 188, 248, 311, 349, 402, 421, 547, 705, 812, 906, 1098, 1162, 1268, 1662
(list; graph; listen)
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OFFSET
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1,3
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LINKS
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C. K. Caldwell, The Prime Glossary, Primeval Number
M. Keith, Integers Containing Many Embedded Primes
G. Villemin's Almanach of Numbers, Primeval Records
Wikipedia, Primeval number.
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EXAMPLE
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The second term in the sequence is 3 because the second primeval number - 13 - can be used to create 3 prime numbers, namely 3, 13 and 31.
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MATHEMATICA
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Needs["DiscreteMath`Combinatorica`"]; f[n_] := Block[{a = Drop[ Sort[ Subsets[ IntegerDigits[n]]], 1], b = c = {}, k = 1, l}, l = Length[a] + 1; While[k < l, b = Append[b, Permutations[ a[[k]] ]]; k++ ]; b = Union[ Flatten[b, 1]]; l = Length[b] + 1; k = 1; While[k < l, c = Append[c, FromDigits[ b[[k]] ]]; k++ ]; Count[ PrimeQ[ Union[c]], True]]; d = -1; Do[ b = f[n]; If[b > d, Print[b]; d = b], {n, 1, 10^6}]
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CROSSREFS
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Cf. A072857, A077623, A076730.
Adjacent sequences: A076494 A076495 A076496 this_sequence A076498 A076499 A076500
Sequence in context: A101762 A139455 A095880 this_sequence A046413 A120635 A113533
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KEYWORD
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more,base,nonn
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AUTHOR
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Lekraj Beedassy (blekraj(AT)yahoo.com), Nov 08 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 12 2002
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