A085133 Numbers n such that n and its digit reversal both are highly composite numbers. Or n and R(n) both are members of A002473.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90, 100, 120, 144, 180, 200, 210, 240, 252, 270, 288, 300, 343, 360, 400, 405, 420, 441, 450, 480, 500, 504, 525, 540, 576, 600, 630, 675, 686, 700, 720

Offset

1,2

Comments

Though a large number of initial terms match, it is different from A005349.

From Robert Israel, Mar 18 2018: (Start)

If n is a term, then so are 10^k*n for all k.

Is a(147)=84672 the last term not divisible by 10? If so, then a(n+43)=10*a(n) for n >= 105. (End)

Links

Robert Israel, Table of n, a(n) for n = 1..1225

Maple

N:= 10^3: # to get all terms <= N (which should be a power of 10)
revdigs:= proc(n) local L;
  L:= convert(n, base, 10);
  add(10^(i-1)*L[-i], i=1..nops(L))
end proc:
S:= {seq(seq(seq(seq(2^a*3^b*5^c*7^d, d=0..floor(log[7](N/(2^a*3^b*5^c)))), c=0..floor(log[5](N/(2^a*3^b)))), b=0..floor(log[3](N/2^a))), a=0..floor(log[2](N)))}:
S:= S intersect map(revdigs, S):
S:= map(t -> seq(t*10^i, i=0..ilog10(N/t)), S):
sort(convert(S, list)); # Robert Israel, Mar 18 2018

Crossrefs

Cf. A005349, A002473.

Sequence in context: A235507 A235697 A085135 * A308560 A285815 A337741

Adjacent sequences: A085130 A085131 A085132 * A085134 A085135 A085136

Keyword

base,nonn

Author

Amarnath Murthy, Jul 06 2003

Extensions

More terms from David Wasserman, Jan 28 2005

Status

approved