OFFSET
1,3
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
M. F. Hasler, Numbers avoiding certain digits OEIS wiki, Jan 12 2020.
FORMULA
a(n) = replace digits d > 6 by d + 1 in base-9 representation of n - 1. - Reinhard Zumkeller, Oct 07 2014
Sum_{n>1} 1/a(n) = A082836 = 22.493475... (Kempner series). - Bernard Schott, Jan 12 2020, edited by M. F. Hasler, Jan 13 2020
MAPLE
a:= proc(n) local l, m; l, m:= 0, n-1;
while m>0 do l:= (d->
`if`(d<7, d, d+1))(irem(m, 9, 'm')), l
od; parse(cat(l))/10
end:
seq(a(n), n=1..100); # Alois P. Heinz, Aug 01 2016
MATHEMATICA
Select[Range[100], DigitCount[#, 10, 7]==0&] (* Harvey P. Dale, Aug 23 2011 *)
PROG
(Magma) [ n: n in [0..89] | not 7 in Intseq(n) ]; // Bruno Berselli, May 28 2011
(sh) seq 0 1000 | grep -v 7; # Joerg Arndt, May 29 2011
(Haskell)
a052419 = f . subtract 1 where
f 0 = 0
f v = 10 * f w + if r > 6 then r + 1 else r where (w, r) = divMod v 9
-- Reinhard Zumkeller, Oct 07 2014
(PARI) lista(nn)=for (n=0, nn, if (!vecsearch(vecsort(digits(n), , 8), 7), print1(n, ", ")); ); \\ Michel Marcus, Feb 22 2015
(PARI) /* See OEIS wiki page for more programs. */
apply( {A052419(n)=fromdigits(apply(d->d+(d>6), digits(n-1, 9)))}, [1..99]) \\ a(n)
next_A052419(n, d=digits(n+=1))={for(i=1, #d, d[i]==7&&return((1+n\d=10^(#d-i))*d)); n} \\ least a(k) > n. Used in A038615. - M. F. Hasler, Jan 11 2020
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Henry Bottomley, Mar 13 2000
EXTENSIONS
Offset changed by Reinhard Zumkeller, Oct 07 2014
STATUS
approved