login
a(n) is the smallest number k such that n consecutive integers starting at k have the same number of odd divisors (A001227).
4

%I #15 Sep 04 2019 08:02:43

%S 1,1,5,10,10,515,2314,2314,1536863,4053992,4053992,18584686,146237365,

%T 163039279,4775943486,13147233734,86153130379

%N a(n) is the smallest number k such that n consecutive integers starting at k have the same number of odd divisors (A001227).

%H Rémy Sigrist, <a href="/A324593/a324593.txt">C program for A324593</a>

%e 515 has 4 odd divisors {1, 5, 103, 515}, 516 has 4 odd divisors {1, 3, 43, 129}, 517 has 4 odd divisors {1, 11, 47, 517}, 518 has 4 odd divisors {1, 7, 37, 259}, 519 has 4 odd divisors {1, 3, 173, 519} and 520 has 4 odd divisors {1, 5, 13, 65}. These the first 6 consecutive numbers with the same number of odd divisors, so a(6) = 515.

%o (C) See Links section.

%Y Cf. A001227, A006558, A045983, A045984, A323253, A324594.

%K nonn,more

%O 1,3

%A _Ilya Gutkovskiy_, Sep 03 2019

%E a(11)-a(14) from _Rémy Sigrist_, Sep 04 2019

%E a(15)-a(17) from _Giovanni Resta_, Sep 04 2019