The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A264440 Row lengths of the irregular triangle A137510 (number of divisors d of n with 1 < d < n, or 0 if no such d exists). 2
 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 2, 3, 1, 4, 1, 4, 2, 2, 1, 6, 1, 2, 2, 4, 1, 6, 1, 4, 2, 2, 2, 7, 1, 2, 2, 6, 1, 6, 1, 4, 4, 2, 1, 8, 1, 4, 2, 4, 1, 6, 2, 6, 2, 2, 1, 10, 1, 2, 4, 5, 2, 6, 1, 4, 2, 6, 1, 10, 1, 2, 4, 4, 2, 6, 1, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS See A032741 for the number of divisors d of n with 1 <= d < n, n >= 1. See A070824 for the number of the divisors d of n with 1 < d < n, n >= 1. LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 FORMULA a(1) = 1; a(n) = 1 if n is prime, otherwise a(n) = A070824(n). a(1) = 1; a(n) = 1 if n is prime, otherwise a(n) = A032741(n) - 1. a(n) = max(1, A000005(n)-2). - Robert Israel, Jan 20 2016 MAPLE seq(max(1, numtheory:-tau(n)-2), n=1..100); # Robert Israel, Jan 20 2016 MATHEMATICA Array[DivisorSigma[0, #] - 2 &, {80}] /. n_ /; n < 2 -> 1 (* Michael De Vlieger, Jan 16 2016 *) PROG (PARI) A264440(n) = max(1, numdiv(n)-2); \\ After Robert Israel's formula. - Antti Karttunen, May 25 2017 CROSSREFS Cf. A000005, A000040, A032741, A070824, A137510. Sequence in context: A194448 A238950 A088433 * A303386 A295636 A050334 Adjacent sequences:  A264437 A264438 A264439 * A264441 A264442 A264443 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Jan 16 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 4 21:43 EDT 2020. Contains 333238 sequences. (Running on oeis4.)