This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A305676 #12 Aug 04 2018 14:45:22 %S A305676 7,24,72,144,240,336,504,720,576,720,1440,2016,2880,4320,5760,10080, %T A305676 10080,10080,10080,8640,8640,10080,17280,15120,17280,17280,17280, %U A305676 20160,30240,40320,60480,120960,181440,241920,362880,483840,725760,1451520,2177280,2419200,2419200 %N A305676 a(n) = A305671(A305672(n)). %C A305676 Do any numbers x exist that never occur in this sequence? Can this be proven for any particular value of x? For example, does 96 occur in this sequence? Note that 96 occurs four times as a value of sigma among the initial 100 composites. %o A305676 (PARI) composite(n) = my(i=0); forcomposite(c=1, , i++; if(i==n, return(c))) %o A305676 mcv(v) = my(w=vecsort(v, , 8), count=vector(#w), ind=0, i=0); for(x=1, #w, for(y=1, #v, if(w[x]==v[y], count[x]++))); for(k=1, #count, if(count[k]==vecmax(count), ind=k; i++)); if(i > 1, return(0), return(w[ind])) %o A305676 a305671(n) = my(v=[]); for(k=1, n, v=concat(v, sigma(composite(k)))); mcv(v) %o A305676 terms(n) = my(x=0, k=1, i=0); while(1, if(a305671(k) > 0, print1(a305671(k), ", "); i++); if(i==n, break); while(a305671(k) > 0, k++); while(a305671(k)==0, k++)) %o A305676 terms(11) \\ Print initial 11 terms of the sequence %Y A305676 Cf. A145899, A305671, A305672, A305673, A305675, A305676. %K A305676 nonn %O A305676 1,1 %A A305676 _Felix Fröhlich_, Jun 08 2018