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A308191
a(n) = smallest m such that A308190(m) = n, or -1 if no such m exists.
4
5, 6, 8, 7, 10, 16, 17, 30, 29, 54, 53, 102, 101, 198, 197, 390, 389, 774, 773, 1542, 3080, 3079, 6154, 12304, 24604, 36901, 73798, 147592, 295180, 295517, 591030, 1182056, 1574849, 3149694, 4728211, 6299383, 12598762, 25197520, 25197533, 50395062, 100790120, 100790119, 201580234, 403160464, 806320924, 1232145821, 2464291638
OFFSET
0,1
COMMENTS
It seems plausible that m exists for all n >= 0.
From Chai Wah Wu, Jun 14 2019: (Start)
All terms are even or prime. If a(n+1) is even, then 2*a(n)-a(n+1) = 4. a(n+1) <= 2*(a(n)-2) and thus m exists for all n >= 0. The proof in the comments of A308193 is applicable for this sequence as well.
If a(n) is prime, then a(n-1) <= a(n) + 1. For the prime terms 7, 17, 29, 53, 101, 197, 389, 773, 3079, 100790119, a(n-1) = a(n) + 1.
(End)
LINKS
CROSSREFS
Sequence in context: A330863 A111514 A308195 * A111770 A105738 A099149
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 14 2019
EXTENSIONS
a(24)-a(41) from Chai Wah Wu, Jun 14 2019
a(42)-a(44) from Chai Wah Wu, Jun 15 2019
a(45)-a(46) from Chai Wah Wu, Jun 16 2019
STATUS
approved