This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A139393 a(n) = Sum_{i=1..m} e(i) * 10^(m-i) where e(1) <= ... <= e(m) are the nonzero exponents in the prime factorization of n: a representation of the prime signature of n. 1
 0, 1, 1, 2, 1, 11, 1, 3, 2, 11, 1, 12, 1, 11, 11, 4, 1, 12, 1, 12, 11, 11, 1, 13, 2, 11, 3, 12, 1, 111, 1, 5, 11, 11, 11, 22, 1, 11, 11, 13, 1, 111, 1, 12, 12, 11, 1, 14, 2, 12, 11, 12, 1, 13, 11, 13, 11, 11, 1, 112, 1, 11, 12, 6, 11, 111, 1, 12, 11, 111, 1, 23, 1, 11, 12, 12, 11, 111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS The sorted sequence of (nonzero) exponents in the prime factorization of a number is called its prime signature. Here this is "approximated" by multiplying them by powers of 10. Up to 2^10 this coincides with the concatenation of these exponents written in base 10 (but that sequence would be "base" specific). For n >= 1024 one should use a modified definition, replacing 10 with 10^floor(1+log_10(log2(n))), to avoid ambiguity of the representation. LINKS Antti Karttunen, Table of n, a(n) for n = 1..1023 E. W. Weisstein, Prime signature on mathworld.wolfram.com. Wikipedia, Prime signature. PROG (PARI) A139393(n)=sum(i=1, #n=vecsort(factor(n)[, 2]), 10^(#n-i)*n[i]) CROSSREFS Cf. A037916, A046523, A101296. Sequence in context: A098290 A160110 A258055 * A037916 A320390 A292355 Adjacent sequences:  A139390 A139391 A139392 * A139394 A139395 A139396 KEYWORD nonn,easy,changed AUTHOR M. F. Hasler, Apr 17 2008, Apr 19 2008 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 December 10 20:53 EST 2019. Contains 329909 sequences. (Running on oeis4.)