OFFSET
1,2
COMMENTS
In other words, k such that row k of the triangle A073029, when converted to a set, does not contain two consecutive numbers.
Since hundred, thousand, million, all contain two consecutive letters, there are no other terms.
REFERENCES
GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See pages 99 and 286.
EXAMPLE
3 is a term because the set {20, 8, 18, 5} (from t,h,r,e,e) does not contain two consecutive numbers.
But 5 is not a term, since e and f are adjacent in the alphabet.
PROG
(Python)
from num2words import num2words as n2w
def ok(n):
w = sorted(c for c in set(n2w(n).replace(" and", "")) if c.isalpha())
return min(ord(w[i+1])-ord(w[i]) for i in range(len(w)-1)) > 1
print([k for k in range(100) if ok(k)]) # Michael S. Branicky, Apr 22 2023
CROSSREFS
KEYWORD
nonn,word,fini,full
AUTHOR
N. J. A. Sloane, Apr 22 2023
EXTENSIONS
Terms 0 and 50 inserted by Michael S. Branicky, Apr 22 2023
STATUS
approved