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Table 1 Identities of divisor functions

From: Convolution identities for twisted Eisenstein series and twisted divisor functions

Identities of convolution sums

Reference

s = 0 k 1 ( 2 k 2 s + 1 ) ( m = 1 N 1 σ 2 k 2 s 1 ( m ) σ 2 s + 1 ( N m ) ) = 2 k + 3 4 k + 2 σ 2 k + 1 ( N ) + ( k 6 N ) σ 2 k 1 ( N ) + 1 2 k + 1 j = 2 k ( 2 k + 1 2 j ) B 2 j σ 2 k + 1 2 j ( N )

[[2], Theorem 12.3]

s = 0 k 1 ( 2 k 2 s + 1 ) ( m = 1 N 1 σ 2 k 2 s 1 ( m ) σ 2 s + 1 ( N m ) ) = 1 2 { σ 2 k + 1 ( N ) N σ 2 k 1 ( N ) }

(10)

s = 0 k 1 ( 2 k 2 s + 1 ) ( m = 1 N σ 2 k 2 s 1 ( 2 m 1 ) σ 2 s + 1 ( 2 N 2 m + 1 ) ) = 1 4 σ 2 k + 1 ( 2 N )

(15)

s = 0 k 1 ( 2 k 2 s + 1 ) m = 1 2 N 1 ( 1 ) m + 1 σ 2 k 2 s 1 ( m ) σ 2 s + 1 ( 2 N m ) = 1 2 ( 2 N σ 2 k 1 ( 2 N ) )

(16)