login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A195165 Starting with 2, successively concatenate the numbers in the prime factorization of a(n-1), including both the prime and its exponent. 0
2, 21, 3171, 31711511, 131171431471711, 16333180310678671, 11117231176912155222911, 1291718606666545569524831, 71131144716241883115716012594411, 11110111723135559111044984144653124782571 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Unlike similar sequences, this sequence does not terminate when a prime is reached; the next term after a prime p is 10*p+1.

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

The factorization of a(2) = 21 is 3^1 * 7^1, so we concatenate 3,1,7,1 to get a(3) = 3171.

MATHEMATICA

NestList[FromDigits[Flatten[IntegerDigits/@FactorInteger[#]]]&, 2, 10] (* Harvey P. Dale, Oct 16 2014 *)

PROG

(PARI) catnum(n, m, b=10)=local(p=1); while(p<=m, p*=b); n*p+m

anext(n, b=10)=local(fm, r); fm=factor(n); for(k=1, matsize(fm)[1], r=catnum(r, catnum(fm[k, 1], fm[k, 2], b), b)); r

CROSSREFS

Cf. A195264, A037274.

Sequence in context: A080815 A276654 A114846 * A201973 A278737 A162393

Adjacent sequences:  A195162 A195163 A195164 * A195166 A195167 A195168

KEYWORD

nonn,base

AUTHOR

Franklin T. Adams-Watters, Sep 14 2011

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 20 10:48 EST 2017. Contains 294963 sequences.