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A117327
Triangular numbers for which the product of the digits is a heptagonal number.
0
0, 1, 10, 36, 105, 120, 136, 171, 190, 210, 300, 406, 630, 703, 780, 820, 903, 990, 1035, 1081, 1540, 1711, 1770, 1830, 2016, 2080, 2701, 2850, 3003, 3081, 3160, 3240, 3321, 3403, 3570, 4005, 4095, 4560, 4950, 5050, 5460, 6105, 6670, 6903, 7021, 7140, 7260
OFFSET
0,3
EXAMPLE
136 is in the sequence because (1) it is a triangular number and (2) the product of its digits 1*3*6=18 is a heptagonal number.
PROG
(PARI) isok(k) = ispolygonal(k, 3) && ispolygonal(vecprod(digits(k)), 7); \\ Michel Marcus, Mar 27 2024
CROSSREFS
Sequence in context: A211057 A118415 A051959 * A153371 A248463 A169880
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
EXTENSIONS
a(24) and a(38) corrected by Georg Fischer, Mar 27 2024
STATUS
approved