[seqfan] Re: A summer seq with second differences

[Aai]

I didn't see a program to generate sequence A226930, so if of any use 
here's a generator in Haskell:

digits = map (fromIntegral.digitToInt). show
inverseDiff xs = scanl (+) (head xs) xs
seqA = iterate ((!!2). iterate inverseDiff. concatMap digits) [1]

Example (executed in GHCi):

~> seqA !!4
[1,2,4,8,16,32,49,72,98,126,158,199,247,297]






On 31-07-13 14:49, Neil Sloane wrote:
> Eric, nice sequence, as always! I added it as A226930.
> I also added your comment to A164073.
> Neil
>
>
> On Tue, Jul 30, 2013 at 3:26 AM, Eric Angelini <Eric.Angelini at kntv.be>wrote:
>
>> Many thanks, Paolo!
>> And such sequences can be computed
>> ad libitum for 3rd, 4th, 5th, ... nth differences, of course.
>>
>> BTW could you add this comment
>> to A164073 (as I have no access to it):
>> "Absolute second differences are the
>> sequence itself"
>> (this might be suggested by the other
>> comments but is not obvious to me).
>>
>> Best,
>> É.
>>
>> Propulsé d'un aPhone
>>
>>
>>
>> Le 30 juil. 2013 à 09:13, "Paolo Lava" <paoloplava at gmail.com> a écrit :
>>
>>> It should start as:
>>>
>>> 1, 2, 4, 8,16, 32, 49, 72, 98, 126, 158, 199, 247, 297, 356, 423, 491,
>> 561,
>>> 637, 714, 796, 886, 977, 1077, 1186, 1297, 1412, 1534, 1658, 1791, 1931,
>>> 2074, 2222, 2376, 2534, 2694, 2857, 3024, 3200, 3377, 3559, 3747, 3936...
>>>
>>>
>>> 2013/7/29 Eric Angelini <Eric.Angelini at kntv.be>
>>>
>>>> Hello SeqFans,
>>>>
>>>> S=1,2,4,8,16,32,49,72,98,126,158,199,247,297,352,423,...
>>>> Compute the second differences and... look who's coming back!
>>>>
>>>> Best,
>>>> É.
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>>
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>>>>
>>> _______________________________________________
>>>
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>> _______________________________________________
>>
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>>
>
>

-- 
Met vriendelijke groet,
@@i = Arie Groeneveld