OFFSET
0,3
COMMENTS
An enneagopnal number is also called a nonagonal number. - Harvey P. Dale, Apr 13 2020
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
EXAMPLE
39804 is in the sequence because (1) it is an enneagonal number,(2)the sum of its digits 3+9+8+0+4=24 is an enneagonal number and (3)the product of its digits 3*9*8*0*4=0 is also an enneagonal number.
MATHEMATICA
With[{nnn=Table[(n(7n-5))/2, {n, 0, 1000}]}, Select[nnn, MemberQ[nnn, Total[ IntegerDigits[ #]]]&&MemberQ[nnn, Times@@IntegerDigits[#]]&]] (* Harvey P. Dale, Apr 13 2020 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 15 2006
STATUS
approved