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A297113
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a(1) = 0, a(2) = 1, after which, a(n) = a(n/2) if n is of the form 4k+2, and otherwise a(n) = 1+a(A252463(n)).
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27
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0, 1, 2, 2, 3, 2, 4, 3, 3, 3, 5, 3, 6, 4, 3, 4, 7, 3, 8, 4, 4, 5, 9, 4, 4, 6, 4, 5, 10, 3, 11, 5, 5, 7, 4, 4, 12, 8, 6, 5, 13, 4, 14, 6, 4, 9, 15, 5, 5, 4, 7, 7, 16, 4, 5, 6, 8, 10, 17, 4, 18, 11, 5, 6, 6, 5, 19, 8, 9, 4, 20, 5, 21, 12, 4, 9, 5, 6, 22, 6, 5, 13, 23, 5, 7, 14, 10, 7, 24, 4, 6, 10, 11, 15, 8, 6, 25
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OFFSET
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1,3
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COMMENTS
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Also the number of squares in the Young diagram of the integer partition with Heinz number n that are graph-distance 1 from the lower-right boundary, where the Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k). For example, the partition (6,5,5,3) with Heinz number 7865 has diagram
o o o o o o
o o o o o
o o o o o
o o o
with inner rim
o
o
o o
o o o
of size 7, so a(7867) = 7.
(End)
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LINKS
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FORMULA
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a(1) = 0, a(2) = 1, after which, a(n) = a(n/2) if n is of the form 4k+2, and otherwise a(n) = 1+a(A252463(n)) .
Other identities. For all n >= 1:
a(A000040(n)) = n. [Each n occurs for the first time at the n-th prime.]
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MATHEMATICA
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Table[If[n==1, 0, PrimePi[FactorInteger[n][[-1, 1]]]+PrimeOmega[n]-PrimeNu[n]], {n, 100}] (* Gus Wiseman, Apr 06 2019 *)
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PROG
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(PARI)
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};
\\ More complex way, after Moebius transform:
(Scheme, with memoization-macro definec)
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CROSSREFS
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One more than A297167 (after the initial term).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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