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@hellman@mathstodon.xyz
Post #2658773
2026-05-06 07:59 UTC
@christianp@mathstodon.xyz Most of the time a(n)=a(n-1)+n, so can be "compressed" by looking into those n where it does not hold. What is interesting, quite many of those actually belong to A395531 itself!
```
n = 3, in A395531? yes, a(n)-a(n-1) = 4 = n + 1
n = 6, in A395531? - , a(n)-a(n-1) = 9 = n + 3
n = 11, in A395531? yes, a(n)-a(n-1) = 14 = n + 3
n = 16, in A395531? yes, a(n)-a(n-1) = 20 = n + 4
n = 22, in A395531? - , a(n)-a(n-1) = 30 = n + 8
n = 32, in A395531? yes, a(n)-a(n-1) = 38 = n + 6
n = 40, in A395531? yes, a(n)-a(n-1) = 47 = n + 7
n = 49, in A395531? yes, a(n)-a(n-1) = 57 = n + 8
n = 59, in A395531? yes, a(n)-a(n-1) = 68 = n + 9
n = 67, in A395531? - , a(n)-a(n-1) = 70 = n + 3
n = 70, in A395531? - , a(n)-a(n-1) = 80 = n + 10
n = 85, in A395531? yes, a(n)-a(n-1) = 96 = n + 11
n = 98, in A395531? yes, a(n)-a(n-1) = 110 = n + 12
```
https://gist.github.com/hellman/a4a56f013085edf379ac6377db0fa9bb
Replies (1)
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@christianp@mathstodon.xyz Some larger values to show that it's still rare:
...
n = 3632, in A395531? yes, a(n)-a(n-1) = 3715 = n + 83
n = 3656, in A395531? - , a(n)-a(n-1) = 3667 = n + 11
n = 3717, in A395531? - , a(n)-a(n-1) = 3801 = n + 84
n = 3814, in A395531? yes, a(n)-a(n-1) = 3899 = n + 85
n = 3901, in A395531? yes, a(n)-a(n-1) = 3987 = n + 86
n = 3989, in A395531? yes, a(n)-a(n-1) = 4076 = n + 87
n = 4078, in A395531? yes, a(n)-a(n-1) = 4166 = n + 88
n = 4168, in A395531? yes, a(n)-a(n-1) = 4257 = n + 89
n = 4259, in A395531? yes, a(n)-a(n-1) = 4349 = n + 90
n = 4351, in A395531? yes, a(n)-a(n-1) = 4442 = n + 91
n = 4444, in A395531? yes, a(n)-a(n-1) = 4536 = n + 92
Open ##2658774