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A342845
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Number of distinct even numbers visible as proper substrings of n.
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4
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 2, 3, 2, 3
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OFFSET
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0,21
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COMMENTS
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Here substrings must be contiguous.
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LINKS
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EXAMPLE
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a(10)=1 because we can form 0.
a(24)=2 because we can form 2, 4.
a(102)=3 because we can form 0, 2, 10.
a(124)=4 because we can form the following even numbers: 2, 4, 12, 24.
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PROG
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(Haskell)
import Data.List (isInfixOf)
a045887 n = length $ filter (`isInfixOf` (show n)) $ map show [0, 2..n-1]
-- Reinhard Zumkeller, Jul 19 2011
(Python)
def a(n):
s, eset = str(n), set()
for i in range(len(s)):
for j in range(i+1, len(s)+1):
if s[j-1] in "02468" and j-i < len(s): # even and proper substring
eset.add(int(s[i:j]))
return len(eset)
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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