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A049053 Numbers n such that n through n+6 all have same number of divisors. 5
171893, 180965, 647381, 1039493, 1071829, 1450261, 1563653, 1713413, 2129029, 2384101, 4704581, 4773301, 5440853, 5775365, 6627061, 6644405, 6697253, 8556661, 8833429, 10531253, 12101509, 12238453, 12307141, 13416661, 13970405 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Allan Swett found that the first term not congruent to 5 mod 16 is 67073285. - Ralf Stephan, Nov 15 2004

Since A119479(n)<7 for n<8, no term has less than 8 divisors; the first that has more is a(30)=17476613. - Ivan Neretin, Feb 05 2016

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

J.-M. De Koninck, Those Fascinating Numbers, Amer. Math. Soc., 2009, page 244.

MAPLE

with(numtheory); A049053:=proc(q, w) local k, ok, n;

for n from 1 to q do ok:=1;

for k from 1 to w do if tau(n)<>tau(n+k) then ok:=0; break; fi; od;

if ok=1 then print(n); fi; od; end: A049053(10^6, 6); # Paolo P. Lava, May 03 2013

PROG

(PARI) isok(n) = {my(nb = numdiv(n)); for (k=1, 6, if (numdiv(n+k) != nb, return (0)); ); 1; } \\ Michel Marcus, Feb 06 2016

CROSSREFS

Cf. A000005, A006558, A019273, A119479.

Other runs of equidivisor numbers: A005237 (runs of 2), A005238 (runs of 3), A006601 (runs of 4), A049051 (runs of 5), A049052 (runs of 6).

Sequence in context: A246227 A206115 A204730 * A242980 A221742 A239789

Adjacent sequences:  A049050 A049051 A049052 * A049054 A049055 A049056

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified March 24 11:49 EDT 2019. Contains 321448 sequences. (Running on oeis4.)