A030455 - OEIS

%I #17 Oct 30 2023 09:53:00

%S 1000000000,2000000000,6000000000,3000000000000,7000000000000,

%T 8000000000000,10000000000001,10000000000002,10000000000006,

%U 10000000000010,11000000000000,12000000000000,20000000000000,30000000000000,80000000000000,90000000000000,3000000000000000

%N Numbers having the same number of digits as letters in their US English spelling.

%C Or, numbers N such that A005589(N)=A055642(N).

%H L. C. Noll, <a href="http://www.isthe.com/cgi-bin/number.cgi">The English name of a number</a>.

%H Wiktionary, <a href="http://en.wiktionary.org/wiki/one_hundred_one">One hundred one</a>.

%e "One billion" has 10 letters and "1000000000" has 10 digits.

%e a(7)=10^13+1 (ten trillion one) has 14 digits and also 14 letters in the US English spelling (while the preferred British spelling is "...and one"). The same applies to a(8)=10^13+2, a(9)=10^13+6, a(10)=10^13+10, a(11)=11*10^12, a(12)=12*10^12, a(13)=20*10^12, a(14)=30*10^12, a(15)=80*10^12, a(16)=90*10^12. - _M. F. Hasler_, Feb 13 2012

%o (PARI) {N=1; while(1, while(0>d=#Str(N*=10)-A005589(N),);

%o d | for(k=1,3,print1(k!*N", ")) | next;  for(k=1,90, for(u=0,90, A005589(k*N+u)==#Str(k*N) & print1(k*N+u","))))}

%Y See A204593 for the French version.

%K nonn,word,base

%O 1,1

%A _Dann Toliver_, 1999

%E Corrected by _M. F. Hasler_, Feb 13 2012