OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Pronic Number
MATHEMATICA
With[{pn=2*Accumulate[Range[430000000]]}, Table[Select[pn, DigitCount[#, 10, 7] == n&, 1], {n, 12}]]//Flatten (* Harvey P. Dale, Aug 14 2017 *)
PROG
(Python)
def A048544(n):
k, m = 1, 2
while True:
if str(m).count('7') == n:
return m
k += 1
m += 2*k # Chai Wah Wu, Mar 23 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1999
EXTENSIONS
a(13)-a(17) from Giovanni Resta, Oct 09 2019
STATUS
approved