A394452 Greater of two consecutive numbers of the form 2^i*5^j with i, j >= 0, that are coprime.

2, 5, 8, 32, 128, 625, 78125, 9765625, 1220703125, 152587890625, 19073486328125, 2384185791015625, 298023223876953125, 37252902984619140625, 4722366482869645213696, 174224571863520493293247799005065324265472, 6462348535570528709932880406796584793482907116413116455078125

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..23

Example

Let s = A003592 and b = A394408.
Table of n, a(n) for n = 1..12:
 n          b(n)     a(n)
----------------------------
 1     s(1) = 1        2
 2     s(3) = 2^2      5
 3     s(4) = 5        2^3
 4     s(9) = 5^2      2^5
 5    s(16) = 5^3      2^7
 6    s(25) = 2^9      5^4
 7    s(68) = 2^16     5^7
 8   s(132) = 2^23     5^10
 9   s(217) = 2^30     5^13
10   s(323) = 2^37     5^16
11   s(450) = 2^44     5^19
12   s(598) = 2^51     5^22

Mathematica

s = With[{nn = 10^80}, Union@ Flatten@ Table[2^i* 5^j, {i, 0, Log2[nn]}, {j, 0, Log[5, nn/2^i] } ] ]; Select[Partition[s, 2, 1], CoprimeQ @@ # &][[;; , -1]]

Crossrefs

Cf. A003592, A186927, A393164, A394408.

Sequence in context: A140275 A025533 A295970 * A086809 A153863 A153890

Adjacent sequences: A394449 A394450 A394451 * A394453 A394454 A394455

Keyword

nonn

Author

Michael De Vlieger, Mar 21 2026

Status

approved