OFFSET
1,2
COMMENTS
LINKS
Frank M Jackson, Table of n, a(n) for n = 1..10000
R. A. Beauregard and E. R. Suryanarayan, Arithmetic Triangles, Mathematics Magazine, pp. 105-115 70(2) 1997 MAA.
FORMULA
n = 1 or a product of primes p congruent to +- 1 (mod 12).
MAPLE
isA072330 := proc(n)
if n = 1 then
true;
else
for p in ifactors(n)[2] do
if not modp(op(1, p), 12) in {1, 11} then
return false ;
end if;
end do:
true;
end if;
end proc:
for n from 1 to 1000 do
if isA072330(n) then
printf("%d, ", n) ;
end if;
end do: # R. J. Mathar, Feb 26 2017
MATHEMATICA
fac12Q[n_] := And @@ (MemberQ[{1, 11}, #] & /@ Mod[First /@ FactorInteger@ n, 12]); Select[Range[600], fac12Q] (* Frank M Jackson, Apr 09 2016 with simplification by Giovanni Resta *)
okQ[n_] := AllTrue[FactorInteger[n][[All, 1]], MatchQ[Mod[#, 12], 1|11]&];
Select[Range[1000], okQ] (* Jean-François Alcover, Mar 06 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, Jul 15 2002
EXTENSIONS
Corrected and extended by Ray Chandler, Jul 02 2004
Incorrect b-file by Carmine Suriano replaced by Frank M Jackson, May 09 2016
STATUS
approved