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Search: id:A125191
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| A125191 |
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Primes of the form k# + (k+1)# +- 1, where k# = A002110(k) = primorial(k). |
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3
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| 2, 7, 37, 239, 241, 2521, 32341, 540539, 540541, 232792559, 232792561, 207030183359, 311671001662019, 41287621429375723111588738861, 5801527386969669153864265802424086050777441586253956297278498679
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Prime numbers n such that n = (prime(k+1) + 1)*k# +- 1 for some k.
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EXAMPLE
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Let k = 1; then 1#+2# = 2+6 = 8, 8-1 = 7 is prime but 8+1 = 9 is nonprime.
Let k = 3; then 3#+4# = 30+210 = 240, 240-1 = 239 is prime and 240+1 = 241 is also prime.
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MAPLE
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A002110 := 1 : A000040 := 2 : for n from 1 to 38 do if isprime(A002110*(1+A000040)-1) then printf("%d, ", A002110*(1+A000040)-1) ; fi ; if isprime(A002110*(1+A000040)+1) then printf("%d, ", A002110*(1+A000040)+1) ; fi ; A002110 := A002110*A000040 : A000040 := nextprime(A000040) : od : - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 26 2007
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PROGRAM
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(PARI) {m=37; for(n=0, m, p=primorial(n)+primorial(n+1); if(isprime(a=p-1), print1(a, ", ")); if(isprime(a=p+1), print1(a, ", ")))} - Klaus Brockhaus, Jan 25 2007
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CROSSREFS
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Cf. A002110 (primorial numbers), A006862 (Euclid numbers), A057588 (Kummer numbers).
Sequence in context: A062394 A063766 A020040 this_sequence A135164 A072597 A125515
Adjacent sequences: A125188 A125189 A125190 this_sequence A125192 A125193 A125194
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KEYWORD
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nonn
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AUTHOR
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Tomas Xordan (xordan.tom(AT)gmail.com), Jan 12 2007
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EXTENSIONS
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Edited, corrected and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 25 2007
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