

A076546


Let P = { p_1 = 3, p_2 = 5, ...} be the set of odd primes. If p_n in P can be written as p_n = q+r+s with q, r, s in P, let a(n) = largest such q, otherwise let a(n) = p_{n+1}.


0



5, 7, 11, 5, 7, 11, 13, 17, 23, 23, 31, 31, 37, 41, 47, 53, 53, 61, 61, 67, 73, 73, 83, 89, 89, 97, 101, 103, 107, 113, 113, 131, 131, 139, 139, 151, 157, 157, 167, 173, 173, 181, 181, 191, 193, 199, 211, 211, 223, 227, 233, 233, 241, 251, 257, 263, 263, 271, 271, 277
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OFFSET

1,1


COMMENTS

11 belongs to a cycle of length 3 when a(n) is iterated. The paper by Janos studies the set of cycles.


REFERENCES

Ludvik Janos, On Vinagradov's 3primes theorem, Abstracts Amer. Math. Soc., 25 (No. 2, 2002), p. 398, #01T1157.


LINKS

Table of n, a(n) for n=1..60.


EXAMPLE

3 has no such representation, so a(1) = 5. The 10th odd prime, 31, equals 23+5+3, with q=23 and no larger q exists, so a(1) = 23.


PROG

(PARI) {forprime(p=3, 300, b=0; q=precprime(p1); while(b<1&&q>2, r=q; while(b<1&&r>2, s=r; while(b<1&&s>2, if(q+r+s==p, b=1; print1(q, ", "), s=precprime(s1))); r=precprime(r1)); q=precprime(q1)); if(b<1, print1(nextprime(p+1), ", ")))}


CROSSREFS

Sequence in context: A061523 A119653 A023592 * A167372 A023590 A096919
Adjacent sequences: A076543 A076544 A076545 * A076547 A076548 A076549


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane, Apr 25 2003


EXTENSIONS

Are there other cycles?  N. J. A. Sloane.
More terms and PARI code from Klaus Brockhaus, Apr 26 2003


STATUS

approved



