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A176657 Numbers k such that prime(k) is not a twin prime and prime(prime(k)) is a twin prime. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

1 is a term because prime(1) = 2 is not a twin prime and prime(prime(1)) = 3 is a twin prime.

MAPLE

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

MATHEMATICA

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-Fran├žois Alcover, Oct 15 2020, after Maple *)

CROSSREFS

Cf. A006450, A007510.

Sequence in context: A306163 A317380 A070572 * A006616 A225929 A179370

Adjacent sequences:  A176654 A176655 A176656 * A176658 A176659 A176660

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Apr 23 2010

EXTENSIONS

Corrected (29 removed, 126 inserted, 202 removed) and extended by R. J. Mathar, Apr 26 2010

STATUS

approved

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Last modified March 9 03:35 EST 2021. Contains 341962 sequences. (Running on oeis4.)