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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A225418 Composite numbers which contain their sum of the distinct prime factors (sopf function) as a substring. 1

%I

%S 25,32,54,98,125,126,128,140,196,230,243,246,255,256,315,322,348,366,

%T 392,512,520,576,625,810,828,896,1024,1029,1060,1080,1152,1166,1216,

%U 1224,1225,1243,1330,1395,1400,1458,1462,1512,1536,1548,1575,1647,1708,1792,1824,1872,1875

%N Composite numbers which contain their sum of the distinct prime factors (sopf function) as a substring.

%H Harvey P. Dale, <a href="/A225418/b225418.txt">Table of n, a(n) for n = 1..1000</a>

%e 17061 is in the sequence because 17061=3*11*11*47, sopf(17061)=3+11+47=61, substring of 17061.

%t Select[Range[2000],CompositeQ[#]&&SequenceCount[IntegerDigits[#], IntegerDigits[ Total[ FactorInteger[#][[All,1]]]]]>0&] (* _Harvey P. Dale_, Apr 29 2018 *)

%o (PARI) sopf(n)= {s=0; f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]); return(s) }

%o Indigit(a,b)={ u=Vec(Str(a));v=Vec(Str(b));indi=0;la=#u;lb=#v;i=1;while(i<=la-lb+1&&indi==0,d=0;for(x=1,lb,if(v[x]==u[i+x-1],d+=1));indi=(d==lb) ;i+=1);return(indi)}

%o { for(i=1,10^4,if(Indigit(i,sopf(i))&&isprime(i)==0,print(i)))}

%K nonn,base

%O 1,1

%A _Antonio Roldán_, May 07 2013

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 15 16:12 EDT 2019. Contains 327078 sequences. (Running on oeis4.)