OFFSET
1,1
COMMENTS
See A020463 for primes.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = f(n+1, 0) with f(n, x) = if n=1 then A004086(x) else f(floor(n/2), 10*x + 3 + 4*(n mod 2)).
MATHEMATICA
Table[FromDigits/@Tuples[{3, 7}, n], {n, 5}]//Flatten (* Harvey P. Dale, Aug 28 2017 *)
PROG
(Haskell)
a143967 = f 0 . (+ 1) where
f y 1 = a004086 y
f y x = f (10 * y + 3 + 4 * r) x' where (x', r) = divMod x 2
-- Reinhard Zumkeller, Mar 18 2015
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Reinhard Zumkeller, Sep 06 2008
STATUS
approved