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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A340592 a(n) is the concatenation of the prime factors (with multiplicity) of n mod n. 5
 0, 0, 2, 0, 5, 0, 6, 6, 5, 0, 7, 0, 13, 5, 14, 0, 17, 0, 5, 16, 13, 0, 15, 5, 5, 9, 3, 0, 25, 0, 14, 14, 13, 22, 1, 0, 29, 1, 25, 0, 27, 0, 11, 20, 39, 0, 47, 28, 5, 11, 29, 0, 11, 16, 43, 34, 55, 0, 15, 0, 45, 22, 14, 58, 1, 0, 41, 47, 47, 0, 57, 0, 15, 55, 15, 18, 51, 0, 65, 12, 77, 0, 53, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 COMMENTS a(n) = 0 if n is prime. The first composite n for which a(n)=0 is 28749. Are there others? There are no other composite n terms for which a(n)=0 up to 5 million. - Harvey P. Dale, Jul 17 2023 LINKS Robert Israel, Table of n, a(n) for n = 2..10000 FORMULA a(n) = A037276(n) mod n. EXAMPLE For n = 20 = 2*2*5, a(20) = 225 mod 20 = 5. MAPLE dcat:= proc(L) local i, x; x:= L[-1]; for i from nops(L)-1 to 1 by -1 do x:= 10^(1+ilog10(x))*L[i]+x od; x end proc: f:= proc(n) local F; F:= sort(ifactors(n)[2], (a, b) -> a[1] < b[1]); dcat(map(t -> t[1]\$t[2], F)) mod n; end proc: map(f, [\$2..100]); MATHEMATICA Table[Mod[FromDigits[Flatten[IntegerDigits/@Table[#[[1]], #[[2]]]&/@FactorInteger[n]]], n], {n, 2, 100}] (* Harvey P. Dale, Jul 17 2023 *) PROG (Python) from sympy import factorint def a(n): if n == 1: return 0 return int("".join(str(f) for f in factorint(n, multiple=True)))%n print([a(n) for n in range(2, 86)]) # Michael S. Branicky, Jan 18 2022 CROSSREFS Cf. A037276, A340594, A340595. Sequence in context: A329375 A078153 A104035 * A326831 A196409 A369909 Adjacent sequences: A340589 A340590 A340591 * A340593 A340594 A340595 KEYWORD nonn,base AUTHOR J. M. Bergot and Robert Israel, Jan 12 2021 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 February 28 08:11 EST 2024. Contains 370393 sequences. (Running on oeis4.)