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A219956 Numbers expressible as 2*p + 3*q in exactly in one way, where p and q are primes. 6
10, 12, 13, 15, 16, 20, 21, 23, 27, 28, 29, 32, 39, 40, 41, 44, 45, 52, 57, 63, 64, 68, 75, 80, 88, 92, 93, 99, 100, 112, 117, 124, 128, 129, 135, 140, 147, 148, 152, 164, 165, 172, 183, 184, 189, 200, 207, 208, 212, 219, 220, 224, 225, 232, 243, 255, 260 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sequence is infinite: All integers of the forms either 2*prime or 3*prime plus 6 are here.

Suggestion: all odd terms are multiples of 3 except for four primes 13, 23, 29, 41.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..10000

EXAMPLE

10 = 2*2 + 3*2, 12 = 2*3 + 3*2, 13 = 2*2 + 3*3.

MATHEMATICA

mx = 260; Sort[First /@ Select[Tally[ Flatten@Table[2 Prime[i] + 3 Prime[k], {k, PrimePi[(mx - 4)/3]}, {i, PrimePi[(mx - 3 Prime[k])/2]}]], #[[2]] < 2 &]]

PROG

(PARI) list(lim)=my(v=vectorsmall(lim\1), u=List()); forprime(p=2, lim\2, forprime(q=2, (lim-2*p)\3, v[2*p+3*q]++)); for(i=1, #v, if(v[i]==1, listput(u, i))); Vec(u) \\ Charles R Greathouse IV, Dec 05 2012

CROSSREFS

Cf. A079026, A219955.

Sequence in context: A031288 A127957 A079026 * A230597 A124867 A199991

Adjacent sequences:  A219953 A219954 A219955 * A219957 A219958 A219959

KEYWORD

nonn

AUTHOR

Zak Seidov, Dec 02 2012

STATUS

approved

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Last modified July 22 14:44 EDT 2019. Contains 325222 sequences. (Running on oeis4.)