A063996 - OEIS

A063996

Numbers k such that ud(k) = sopf(k)-1, where ud(k)=A034444(k) and sopf(k)=A008472(k).

3, 6, 9, 12, 18, 24, 27, 36, 48, 54, 72, 81, 96, 108, 144, 162, 192, 210, 216, 243, 288, 324, 384, 420, 432, 486, 576, 630, 648, 729, 768, 840, 864, 972, 1050, 1152, 1260, 1296, 1458, 1470, 1536, 1680, 1728, 1890, 1944, 2100, 2187, 2304, 2520, 2592, 2916

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (term 1..1000 from Harry J. Smith)

PROG

(PARI) sopf(n, s, fac, i)=fac=factor(n); for(i=1, matsize(fac)[1], s=s+fac[i, 1]); return(s); ud(n) = 2^omega(n); j=[]; for(n=1, 7000, if(ud(n)==sopf(n)-1, j=concat(j, n))); j

(PARI) sopf(n)= { local(f, s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]); return(s) } { n=0; for (m=1, 10^9, if (2^omega(m)==sopf(m) - 1, write("b063996.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Sep 05 2009

CROSSREFS

Cf. A034444, A008472.

Sequence in context: A231960 A052287 A156997 * A065119 A293396 A173195

Adjacent sequences: A063993 A063994 A063995 * A063997 A063998 A063999

KEYWORD

easy,nonn

AUTHOR

Jason Earls, Sep 06 2001

STATUS

approved