

A181994


Initial members of prime triples p < q < r such that rq = n*(qp).


2



3, 2, 29, 8117, 137, 197, 45433, 1931, 521, 156151, 1949, 1667, 480203, 2969, 7757, 2181731, 12161, 28349, 6012893, 20807, 16139, 3933593, 163061, 86627, 13626251, 25469, 40637, 60487753, 79697, 149627, 217795241, 625697, 552401, 240485251, 173357, 360089, 122164741
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OFFSET

1,1


COMMENTS

For some n, a(n) are abnormally large: note, e.g., that if qp=2, then n cannot be of the form 4+3k, that is why a(4), a(7), a(10), ... are larger than neighbor terms; also, a(67) > 1.1*10^11. Is the sequence infinite?


LINKS

Zak Seidov, Table of n, a(n) for n = 1..66


FORMULA

a(n) = prevprime(A179210(n)).  Robert G. Wilson v, Dec 23 2016


EXAMPLE

First 10 cases of {n,p,q,r}: {1,3,5,7}, {2,2,3,5}, {3,29,31,37}, {4,8117,8123,8147}, {5,137,139,149}, {6,197,199,211}, {7,45433,45439,45481}, {8,1931,1933,1949}, {9,521,523,541}, {10,156151,156157,156217}.


CROSSREFS

Particular cases with qp=2: A022004 [(rq)=2*(qp)], A049437 [rq)=3*(qp) starting with 2nd term].
Cf. A179210.
Sequence in context: A065353 A046272 A054676 * A154332 A252595 A292158
Adjacent sequences: A181991 A181992 A181993 * A181995 A181996 A181997


KEYWORD

nonn


AUTHOR

Zak Seidov, May 31 2012


STATUS

approved



