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A077395 Lesser of two successive squarefree numbers whose product is not squarefree. 3
174, 422, 474, 602, 831, 843, 930, 1074, 1182, 1322, 1374, 1443, 1518, 1623, 1803, 1974, 2006, 2022, 2222, 2274, 2298, 2522, 2526, 2595, 2694, 2870, 2874, 3122, 3210, 3282, 3423, 3478, 3574, 3702, 3770, 3774, 4022, 4074, 4202, 4323, 4359, 4458, 4474 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Squarefree numbers b(m) = A005117(m) such that gcd(b(m),b(m+1)) > 1. - Thomas Ordowski, Aug 15 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

Conjecture: lim_{n->oo} n/a(n) > 0. - Thomas Ordowski and Robert Israel, Aug 18 2015

EXAMPLE

A005117(106)*A005117(107) = 174*177 = (2*3*29)*(3*59) is not squarefree, therefore 174 is a term.

MAPLE

SF:= select(numtheory:-issqrfree, [$1..10000]):

map(t -> if igcd(SF[t], SF[t+1])>1 then SF[t] else NULL fi, [$1..nops(SF)-1]); # Robert Israel, Aug 16 2015

MATHEMATICA

Transpose[Select[Partition[Select[Range[5000], SquareFreeQ], 2, 1], !SquareFreeQ[ Times@@#]&]][[1]] (* Harvey P. Dale, Dec 14 2012 *)

PROG

(PARI) lista(nn) = {last = 2; for (n=3, nn, if (issquarefree(n), if (! issquarefree(last*n), print1(last, ", ")); last = n; ); ); } \\ Michel Marcus, Aug 17 2015

CROSSREFS

Cf. A076144.

Sequence in context: A168349 A179136 A249432 * A185534 A185526 A248458

Adjacent sequences:  A077392 A077393 A077394 * A077396 A077397 A077398

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 04 2002

STATUS

approved

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Last modified September 15 20:11 EDT 2019. Contains 327086 sequences. (Running on oeis4.)