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A088364 a(n) = index of the n-th local minimum of A053707. 2
1, 3, 6, 9, 13, 16, 19, 21, 26, 28, 30, 33, 37, 39, 43, 48, 50, 53, 56, 61, 63, 66, 68, 70, 73, 75, 78, 80, 82, 86, 90, 94, 96, 98, 102, 105, 108, 112, 115, 119, 124, 128, 132, 134, 136, 139, 141, 144, 146, 148, 150, 152, 156, 158, 160, 165, 168, 171, 173, 176, 180, 182 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
A053707(a(n)) = A088363(n).
EXAMPLE
The eighth local minimum of A053707 is 17 and occurs at index 21, hence a(8) = 21; A053707(a(8)) = A053707(21)) = 17 = A088363(8).
MAPLE
N:= 10^6: # to use values of A025475 up to N
P:= select(isprime, [2, seq(i, i=3..isqrt(N), 2)]):
B:= sort([1, seq(seq(p^i, i=2..ilog[p](N)), p=P)]):
DB:= B[2..-1]-B[1..-2]:
T:= select(t -> DB[t] <= DB[t-1] and DB[t] <= DB[t+1], [$2..nops(DB)-1]):
[1, op(T)]; # Robert Israel, Aug 21 2023
PROG
(PARI) {m=1; k=0; for(n=2, 530000, if(matsize(factor(n))[1]==1&&factor(n)[1, 2]>1, d=n-m; if((k<2||b>c)&&(!k<1&&d>=c), print1(k, ", ")); k++; m=n; b=c; c=d))}
CROSSREFS
Sequence in context: A338763 A159908 A236761 * A022853 A198264 A186516
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Sep 27 2003
STATUS
approved

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Last modified February 28 13:34 EST 2024. Contains 370400 sequences. (Running on oeis4.)