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A270003 Least prime p such that n = p + q - r for some primes q and r with q > p. 5
3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

p = 3 when n is an odd nonprime and p = 2 otherwise, so that 3 appears in positions given by A014076.

LINKS

Clark Kimberling, Table of n, a(n) for n = 1..10000

EXAMPLE

n   p   q   r

1   3   5   7

2   2   3   3

3   2   3   2

4   2   5   3

5   2   5   2

6   2   7   3

7   2   7   2

MATHEMATICA

t = Join[{{1, {3, 5, 7}}, {2, {2, 3, 3}}}, Table[If[PrimeQ[n], {n, {2, n, 2}}, p = If[EvenQ[2 + NextPrime[n, 1] - n], 3, 2]; NestWhile[# + 1 &, 1, ! PrimeQ[r = (p + (q = NextPrime[n, #])) - n] &]; {n, {p, q, r}}], {n, 3, 300}]];

Map[#[[2]][[1]] &, t] (* p, A270003 *)

Map[#[[2]][[2]] &, t] (* q, A270753 *)

Map[#[[2]][[3]] &, t] (* r, A271353 *)

(* Peter J. C. Moses, Apr 26 2016 *)

PROG

(PARI) a(n)=if(n%2 && !isprime(n), 3, 2) \\ Charles R Greathouse IV, Apr 29 2016

CROSSREFS

Cf. A000040, A270753, A271353.

Sequence in context: A248743 A085398 A252503 * A067438 A178250 A174550

Adjacent sequences:  A270000 A270001 A270002 * A270004 A270005 A270006

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Apr 26 2016

STATUS

approved

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Last modified March 28 07:59 EDT 2020. Contains 333079 sequences. (Running on oeis4.)