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A116283 k times k+7 gives the concatenation of two numbers m and m-1. 5
7, 30, 64, 42753, 57241, 75423, 425072, 574922, 979528, 4301393, 5698601, 7028666, 4925000747, 5074999247, 7748266574, 8511881484, 8814851184, 7059602159672, 7106167933828, 7439286611621, 7485852385777 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
PROG
(Python)
def ok(n):
s = str(n*(n+7)); h = (len(s)+1)//2; return int(s[:h])-1 == int(s[h:])
print(list(filter(ok, range(2, 10**6)))) # Michael S. Branicky, Jul 30 2021
CROSSREFS
Sequence in context: A018831 A063128 A063148 * A139274 A086640 A083474
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
STATUS
approved

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Last modified May 22 11:13 EDT 2024. Contains 372745 sequences. (Running on oeis4.)