Gah, these number sequences are just too boring! You just plug them in and then you're done!

There is a function $f : \mathcal{S} \to \mathbb{Z}$, where $\mathcal{S}$ is a finite subset of the positive integers that are $10 \pmod{16}$. It is known that $$f(59188506) = 127, ~f(101156906) = 108, ~f(51786282)=112, ~f(72562458)=97.$$

In addition, for many of the elements in $\mathcal{S}$, the value of $f$ is either zero or one.

What is $f$?

  • $\begingroup$ Truly, a very nice "number sequence puzzle"! $\endgroup$ Feb 27, 2022 at 3:31

1 Answer 1


$f(n)$ is the function which

takes the hexadecimal representation of $n$, reverses it, and if the result is a valid A-number for an OEIS entry, returns the first member of the corresponding sequence.


$59188506_{10} = 387251A_{16}$, and A152783 begins $\boxed{127}, 607, 4423, \dots$
$101156906_{10} = 607882A_{16}$, and A288706 begins $\boxed{108}, 614, 3840, \dots$
$51786282_{10} = 316322A_{16}$, and A223613 begins $\boxed{112}, 6592, 124672, \dots$
$72562458_{10} = 453371A_{16}$, and A173354 begins $\boxed{97}, 37840, 199652, \dots$

  • $\begingroup$ That's it, great job! $\endgroup$
    – flame
    Feb 27, 2022 at 5:11

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