OFFSET
1,2
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..10000
MAPLE
with(numtheory): A190308 := proc(n) option remember: local k, t: if(n=1)then return 1: fi: for k from procname(n-1)+1 do t:=tau(4*k-1): if(t=tau(4*k+1) and t=tau(6*k-1) and t=tau(6*k+1))then return k: fi: od: end: seq(A190308(n), n=1..50); # Nathaniel Johnston, May 25 2011
MATHEMATICA
d[n_] := d[n] = DivisorSigma[0, n]; Select[Range[1600], d[4*#-1] == d[4*#+1] == d[6*#-1] == d[6*#+1] &] (* Amiram Eldar, Dec 02 2023 *)
PROG
(PARI) is(n) = {my(d = numdiv(4*n-1)); numdiv(4*n+1) == d && numdiv(6*n-1) == d && numdiv(6*n+1) == d; } \\ Amiram Eldar, Dec 02 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, May 08 2011
EXTENSIONS
Terms after a(10) from Nathaniel Johnston, May 25 2011
STATUS
approved