OFFSET
1,2
COMMENTS
a(n) is the union of A176555(n) for n >= 1 and A176556(n) for n >= 2. See A176553 (numbers m such that concatenations of divisors of m are noncomposites) and A176554 (numbers m such that concatenations of divisors of m are nonprimes). [Jaroslav Krizek, Apr 21 2010]
a(n) is the concatenation of n-th row of the triangle in A027750.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
a[n_] := ToExpression[ StringJoin[ ToString /@ Divisors[n] ] ]; Table[ a[n], {n, 1, 34}] (* Jean-François Alcover, Dec 01 2011 *)
FromDigits[Flatten[IntegerDigits/@Divisors[#]]]&/@Range[40] (* Harvey P. Dale, Nov 09 2012 *)
PROG
(Haskell)
a037278 = read . concatMap show . a027750_row :: Integer -> Integer
-- Reinhard Zumkeller, Jul 13 2013, May 01 2012, Aug 07 2011
(PARI) a(n) = my(s=""); fordiv(n, d, s = concat(s, Str(d))); eval(s); \\ Michel Marcus, Jun 01 2019 and Sep 22 2022
(Magma) k:=1; sol:=[];
for u in [1..34] do D:=Divisors(u); conc:=D[1];
for u1 in [2..#D] do a:=#Intseq(conc); a1:=#Intseq(D[u1]); conc:=10^a1*conc+D[u1]; end for;
sol[u]:=conc; k:=k+1;
end for;
sol; // Marius A. Burtea, Jun 01 2019
(MATLAB) m=1;
for u=1:34 div=divisors(u); conc=str2num(strrep(num2str(div), ' ', ''));
sol(m)=conc; m=m+1;
end
sol % Marius A. Burtea, Jun 01 2019
(Python)
from sympy import divisors
def a(n): return int("".join(str(d) for d in divisors(n)))
print([a(n) for n in range(1, 35)]) # Michael S. Branicky, Dec 31 2020
KEYWORD
nonn,easy,base,nice,changed
AUTHOR
EXTENSIONS
More terms from Erich Friedman
STATUS
approved