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A079026 Numbers that can be represented as 2*p + 3*q, where p and q are prime. 8
10, 12, 13, 15, 16, 19, 20, 21, 23, 25, 27, 28, 29, 31, 32, 35, 37, 39, 40, 41, 43, 44, 45, 47, 49, 52, 53, 55, 57, 59, 61, 63, 64, 65, 67, 68, 71, 73, 75, 77, 79, 80, 83, 85, 88, 89, 91, 92, 93, 95, 97, 99, 100, 101, 103, 107, 109, 112, 113, 115, 117, 119, 121, 124, 125, 127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The primes p and q may be the same.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = 2*p + 3*q, for some primes p and q.

a(n) > 3n + O(n/log n). - Charles R Greathouse IV, Dec 04 2012

EXAMPLE

13 = 2*2 + 3*3, with p = 2 and q = 3.

MATHEMATICA

mx = 130; Union@ Flatten@ Table[ 2Prime[i] + 3Prime[j], {i, PrimePi[mx/2]}, {j, PrimePi[(mx - 2Prime[i])/3]}] (* Robert G. Wilson v, Dec 12 2012 *)

PROG

(PARI) for(i=1, 200, for(j=1, i/2, k=floor((i-2*j)/3); if(i-2*j-3*k, if(isprime(j), if(isprime(k), print(i); break, )))))

(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]=1)); for(i=1, #v, if(v[i], listput(u, i))); Vec(u) \\ Charles R Greathouse IV, Dec 03 2012

CROSSREFS

Sequence in context: A124404 A031288 A127957 * A219956 A230597 A124867

Adjacent sequences:  A079023 A079024 A079025 * A079027 A079028 A079029

KEYWORD

easy,nonn

AUTHOR

Randy L. Ekl, Feb 01 2003

EXTENSIONS

Missing term, 100 (equal to 2 * 47 + 3 * 2), added by Zak Seidov, Dec 02 2012

STATUS

approved

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)