OFFSET
1,1
COMMENTS
Written in Roman numerals this sequence begins II, V, XI, LIX, CI, DIX, MIX, MLI, MMMI.
For a while I actually considered putting in 97 (XCVII) instead of 101 (CI), since XCVII contains CI as a substring. But it also contains II, V and XI as substrings, so going in order strictly from smallest to greatest, 97 must be excluded.
EXAMPLE
a(4) = 59 because it is a prime number and in Roman numerals it's written LIX (all the substrings are composite or not prime: L, LI, LX, I, IX, X).
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert Happelberg (roberthappelberg(AT)yahoo.com), Jul 27 2007
STATUS
approved