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A109020 (2*7^n - 3*3^n + 1)/6. 1
0, 1, 12, 101, 760, 5481, 38852, 273421, 1918320, 13441361, 94128892, 659020341, 4613496680, 32295539641, 226071966132, 1582513328861, 11077621999840, 77543440092321, 542804338926572, 3799631147326981, 26597420355811800, 186181949464251401, 1303273667170466212 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

COMMENTS

Number of incongruent integer-edged Heron triangles whose circumdiameter is the product of n distinct primes of shape 4k + 1.

CROSSREFS

Sequence in context: A016283 A199681 A008547 * A099299 A022736 A082151

Adjacent sequences:  A109017 A109018 A109019 * A109021 A109022 A109023

KEYWORD

nonn

AUTHOR

Alex Fink and R. K. Guy, Aug 18 2005

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Last modified February 17 04:58 EST 2012. Contains 205985 sequences.