The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A305196 a(n) is the smallest number k such that tau(k + n) = tau(k) + n where tau(n) is the number of divisors of n (A000005). 2
 1, 1, 10, 9, 26, 25, 74, 29, 82, 441, 170, 133, 348, 131, 166, 3025, 344, 559, 1602, 557, 820, 9979, 986, 4333, 1236, 9191, 694, 3249, 1652, 3481, 9378, 34969, 3118, 249967, 5636, 36829, 3324, 51947, 3994, 6561, 5000, 15835, 16806, 3557, 6436, 119025, 6254, 589777, 7512, 1768851 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Michel Marcus and Giovanni Resta, Table of n, a(n) for n = 0..244 (terms up to a(106) from Michel Marcus) EXAMPLE 10 and 12 have respectively 4 and 6 divisors, that is, 12-10 = 6-4, so a(2)=10. 9 and 12 have respectively 3 and 6 divisors, that is, 12-9 = 6-3, so a(3)=9. MAPLE f:= proc(n) local k; for k from 1 do if numtheory:-tau(k+n)=numtheory:-tau(k)+n then return k fi od end proc: map(f, [\$0..50]); # Robert Israel, May 28 2018 MATHEMATICA Array[Block[{k = 1}, While[DivisorSigma[0, k + #] != DivisorSigma[0, k] + #, k++]; k] &, 40, 0] (* Michael De Vlieger, May 27 2018 *) PROG (PARI) a(n) = {my(k=1); while(numdiv(k+n) != numdiv(k) + n, k++); k; } CROSSREFS Cf. A000005, A099642, A015886 (similar, with sigma). Sequence in context: A184959 A309661 A003568 * A099642 A271973 A237114 Adjacent sequences: A305193 A305194 A305195 * A305197 A305198 A305199 KEYWORD nonn AUTHOR Michel Marcus, May 27 2018 STATUS approved

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

Last modified March 4 22:06 EST 2024. Contains 370532 sequences. (Running on oeis4.)