OFFSET
1,2
REFERENCES
M. J. Halm, Sequences (Re)discovered, Mpossibilities 81 (Aug. 2002).
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000
PROG
(PARI) is(n)=!setintersect(Set(Vec(English(n))), ["r", "u"]) \\ See A052360 for English(). - M. F. Hasler, Apr 01 2019
/* Alternate code, not using English(): (valid for 1 <= n < one trillion, which should be forbidden due to the 'r' but returns 1) */
is(n)={setintersect( Set(digits(n)), [3, 4]) && return; !while(n=divrem(n, 10^6), n[2]<100||return; n=n[1])} \\ M. F. Hasler, Apr 01 2019
(Python)
from num2words import num2words
from itertools import islice, product
def ok(n): return set(num2words(n)) & {"r", "u"} == set()
def agen(): # generator of terms < 10**304
base, pows = [k for k in range(1, 1000) if ok(k)], [1]
yield from ([0] if ok(0) else []) + base
for e in range(3, 304, 3):
if set(num2words(10**e)[4:]) & {"r", "u"} == set():
pows = [10**e] + pows
for t in product([0] + base, repeat=len(pows)):
if t[0] == 0: continue
yield sum(t[i]*pows[i] for i in range(len(t)))
print(list(islice(agen(), 66))) # Michael S. Branicky, Aug 19 2022
CROSSREFS
KEYWORD
easy,nonn,word
AUTHOR
Michael Joseph Halm, Aug 13 2002
EXTENSIONS
Missing term 52 inserted by Michael S. Branicky, Aug 19 2022
STATUS
approved