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A154952 Index of first occurrence of n in A154404. 1


%S 1,5,6,7,12,9,13,17,22,20,26,56,50,46,74,106,76,152,116,242,206,284,

%T 623,1056,1032,1582,1586,1616,1892,1676,4286,5484,4946,7016,5366,

%U 11262,18776,17486,19688,18192,21018,60662,51476,56546,79946,66986,105476

%N Index of first occurrence of n in A154404.

%C A related problem is to determine the index of the last occurrence of n in A154404. Among the first 10^6 terms in A154404, the values 0, 1, 2 and 3 last occur at indices 4, 5, 6 and 8, respectively, but all values larger than 3 that occur at all (4 through 56 and 58 through 61) do so at least once beyond the 500000th term.

%C The value 4, after its initial occurrence in A154404 at n=12, does not reoccur until n=666393. (The 4 ways to reach 666393 as a sum of an odd prime, a positive Fibonacci number and a Catalan number are 605023+2584+58786, 606997+610+58786, 607573+34+58786 and 648677+17711+5.)

%e a(4) = 12 because 12 is the smallest number that can be expressed in exactly 4 ways as the sum of an odd prime, a positive Fibonacci number and a Catalan number. (The 4 ways are 3+8+1, 5+2+5, 5+5+2 and 7+3+2.)

%Y Cf. A154404

%K nonn

%O 0,2

%A _Jon E. Schoenfield_, Jan 18 2009

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Last modified December 8 08:31 EST 2021. Contains 349594 sequences. (Running on oeis4.)