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A187766 Even numbers k such that prime(k) -+ k are both composite. 0
12, 20, 36, 38, 40, 46, 52, 56, 58, 60, 62, 64, 74, 78, 80, 86, 88, 112, 118, 120, 122, 124, 128, 132, 134, 136, 138, 140, 142, 146, 156, 160, 162, 164, 166, 170, 176, 182, 184, 186, 188, 190, 194, 198, 208, 210, 212, 216 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Even numbers not in A064269 and not in A064402.

Interestingly, prime(12) = 37 and both 37 - 12 = 25 and 37 + 12 = 49 are squares. Is there another such n?

LINKS

Table of n, a(n) for n=1..48.

MATHEMATICA

Select[2*Range[200], !PrimeQ[Prime[#]+#]&&!PrimeQ[Prime[#]-#]&] (* Harvey P. Dale, Dec 24 2013 *)

PROG

(PARI) {forstep(i=2, 220, 2, p=prime(i); if(!isprime(p-i)&&!isprime(p+i), print1(i", ")))}

CROSSREFS

Cf. A064269, A064402.

Sequence in context: A026041 A299028 A082296 * A260905 A211415 A209973

Adjacent sequences:  A187763 A187764 A187765 * A187767 A187768 A187769

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 04 2013

STATUS

approved

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Last modified August 25 21:00 EDT 2019. Contains 326324 sequences. (Running on oeis4.)