OFFSET
1,3
EXAMPLE
7337 is in the sequence because (1) it is an icosagonal number and (2) the sum of the digits 7+3+3+7=20 is also an icosagonal number.
PROG
(PARI) isok(n) = ispolygonal(n, 20) && ispolygonal(sumdigits(n), 20); \\ Michel Marcus, Feb 27 2014
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006
EXTENSIONS
a(11) corrected by Georg Fischer, Mar 27 2024
STATUS
approved