A049053 Numbers k such that k through k+6 all have the same number of divisors.

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

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 fewer than 8 divisors; the first that has more is a(30)=17476613. - Ivan Neretin, Feb 05 2016

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Donovan Johnson)

Jean-Marie De Koninck, Those Fascinating Numbers, Amer. Math. Soc., 2009, page 244.

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,changed

Author

David W. Wilson

Status

approved