OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).
EXAMPLE
336 = sigma(132) = sigma(140) = sigma(182) = sigma(188) = sigma(195) = sigma(249) = sigma(287) = sigma(299).
MAPLE
N:= 30000: # to get terms <= N
V:= Vector(N):
for k from 1 to N-1 do
t:= numtheory:-sigma(k);
if t <= N then V[t]:= V[t]+1 fi
od:
select(t -> V[t]=8, [$1..N]); # Robert Israel, Sep 22 2019
MATHEMATICA
a = Table[ 0, {20000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 20001, a[ [ s ] ]++ ], {n, 1, 20000} ]; Select[ Range[ 20000 ], a[ [ # ] ] == 8 & ]
PROG
(PARI) is(k) = invsigmaNum(k) == 8 \\ Amiram Eldar, Nov 18 2024, using Max Alekseyev's invphi.gp
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 18 2001
STATUS
approved