OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..500
Antonio Roldán, hojaynumeros.blogspot.com
Wikipedia, Additive function
EXAMPLE
308 is a term because bigomega(308)=4 (308=2*2*7*11), 308 + 4 = 312, sopfr(308) = 2 + 2 + 7 + 11 = 22, 312 = 2*2*2*3*13, sopfr(312) = 2 + 2 + 2 + 3 + 13 = 22.
MAPLE
A001414 := proc(n) if n = 1 then 0; else f := ifactors(n)[2] ; add( op(1, i)*op(2, i), i=f) ; end if; end proc:
for n from 1 to 50000 do if isA187877(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Mar 14 2011
MATHEMATICA
soprQ[n_]:=Total[Flatten[Table[#[[1]], {#[[2]]}]&/@FactorInteger[n]]] == Total[Flatten[Table[#[[1]], {#[[2]]}]&/@FactorInteger[n+PrimeOmega[n]]]]; Select[Range[50000], soprQ] (* Harvey P. Dale, Jan 21 2013 *)
PROG
(PARI)
sopfr(n)= { local(f, s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]*f[i, 2]); return(s) }
{ for (n=1, 10^6, if (sopfr(n)==sopfr(n+bigomega(n)), print1(n, ", "))); }
/* Antonio Roldán, Oct 23 2012 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Mar 14 2011
STATUS
approved