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A176657
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Numbers k such that prime(k) is not a twin prime and prime(prime(k)) is a twin prime.
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1
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1, 16, 23, 24, 30, 40, 55, 56, 59, 63, 68, 71, 74, 80, 87, 93, 95, 103, 106, 107, 108, 112, 118, 122, 126, 128, 129, 132, 136, 137, 150, 159, 169, 187, 188, 193, 199, 244, 248, 258, 267, 271, 276, 281, 284, 285, 292, 299, 300, 304, 310, 311, 312, 317, 325, 327
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OFFSET
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1,2
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LINKS
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Robert Israel, Table of n, a(n) for n = 1..10000
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EXAMPLE
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1 is a term because prime(1) = 2 is not a twin prime and prime(prime(1)) = 3 is a twin prime.
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MAPLE
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A006450 := proc(n) ithprime(ithprime(n)) ; end proc: isA176657 := proc(n) isA007510(ithprime(n)) and not isA007510(A006450(n)) ; end proc: for n from 1 to 1600 do if isA176657(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Apr 26 2010
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MATHEMATICA
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A006450[n_] := Prime[Prime[n]];
isA007510[n_] := !PrimeQ[n-2] && !PrimeQ[n+2];
isA176657[n_] := isA007510[Prime[n]] && !isA007510[A006450[n]];
Reap[For[n = 1, n <= 1000, n++, If[isA176657[n], Sow[n]]]][[2, 1]] (* Jean-François Alcover, Oct 15 2020, after Maple *)
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CROSSREFS
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Cf. A006450, A007510.
Sequence in context: A306163 A317380 A070572 * A006616 A225929 A179370
Adjacent sequences: A176654 A176655 A176656 * A176658 A176659 A176660
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov, Apr 23 2010
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EXTENSIONS
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Corrected (29 removed, 126 inserted, 202 removed) and extended by R. J. Mathar, Apr 26 2010
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STATUS
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approved
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